diff --git a/.github/workflows/_reusable_check.yml b/.github/workflows/_reusable_check.yml
index ed733fa..5f1dcf8 100644
--- a/.github/workflows/_reusable_check.yml
+++ b/.github/workflows/_reusable_check.yml
@@ -25,6 +25,9 @@ jobs:
       - name: Biome Check
         run: npm run check
 
+      - name: Test
+        run: npm test
+
       - name: TypeCheck
         run: npm run typecheck
 
diff --git a/.github/workflows/_reusable_lambda_rie_test.yml b/.github/workflows/_reusable_lambda_rie_test.yml
index 940037c..782dad8 100644
--- a/.github/workflows/_reusable_lambda_rie_test.yml
+++ b/.github/workflows/_reusable_lambda_rie_test.yml
@@ -18,7 +18,7 @@ jobs:
       - run: npm ci
 
       - name: Bundle handler
-        run: npx esbuild index.ts --bundle --platform=node --target=node24 --external:@slack/bolt --outfile=dist/index.js
+        run: npx esbuild src/handler.ts --bundle --platform=node --target=node24 --external:@slack/bolt --outfile=dist/index.js
 
       - name: Prepare Lambda artifact
         run: cp -R node_modules dist/
diff --git a/index.ts b/index.ts
deleted file mode 100644
index 949b735..0000000
--- a/index.ts
+++ /dev/null
@@ -1,91 +0,0 @@
-// index.ts
-import { App, AwsLambdaReceiver } from '@slack/bolt';
-import type { GenericMessageEvent } from '@slack/types';
-
-const SLACK_SIGNING_SECRET = process.env['SLACK_SIGNING_SECRET'];
-if (!SLACK_SIGNING_SECRET) throw new Error('signing secret is undefined');
-
-// AWS Lambdaのレシーバーを作成
-const awsLambdaReceiver = new AwsLambdaReceiver({
-	signingSecret: SLACK_SIGNING_SECRET,
-});
-
-// Slack Appの設定情報
-const app = new App({
-	token: process.env['SLACK_BOT_TOKEN'],
-	receiver: awsLambdaReceiver,
-});
-
-const TIMES_ALL_CHANNEL_ID = process.env['TIMES_ALL_CHANNEL_ID']; // `times-all` チャンネルのIDを設定
-if (!TIMES_ALL_CHANNEL_ID) throw new Error('times-all channel is undefined');
-const WORKSPACE_URL = process.env['WORKSPACE_URL']; // SlackワークスペースのURLを設定
-if (!WORKSPACE_URL) throw new Error('workspace is undefined');
-
-// 型ガード関数
-function isGenericMessageEvent(event: unknown): event is GenericMessageEvent {
-	return (event as GenericMessageEvent).type === 'message';
-}
-
-// 'times-'プレフィックスがついたチャンネルのメッセージを検出
-app.message(async ({ message, client }) => {
-	console.log('received message');
-	if (!isGenericMessageEvent(message)) {
-		console.log('not a message event');
-		return;
-	}
-	// メッセージがチャンネルからのものかどうか確認
-	if (
-		'channel' in message &&
-		message.channel_type === 'channel' &&
-		message.channel !== TIMES_ALL_CHANNEL_ID
-	) {
-		console.log('time-all以外のチャンネル');
-		// チャンネルの情報を取得
-		const channelInfo = await client.conversations.info({
-			channel: message.channel,
-		});
-		console.log('channelInfo:', channelInfo);
-		// チャンネル名が'times-'で始まる場合、メッセージを'times-all'に転載
-		if (channelInfo.channel?.name?.startsWith('times-')) {
-			console.log('channel name starts with times-');
-			if ('hidden' in message) {
-				return;
-			} //hidden subtypeがある場合は無視
-			// https://api.slack.com/events/message#hidden_subtypes
-			if ('subtype' in message && message.subtype === 'channel_join') {
-				return;
-			} //チャンネル参加メッセージは無視
-			const messageTimestamp = message.ts.replace('.', '');
-			const messageLink = `${WORKSPACE_URL}/archives/${message.channel}/p${messageTimestamp}`;
-			console.log('messageLink:', messageLink);
-			await client.chat.postMessage({
-				channel: TIMES_ALL_CHANNEL_ID,
-				text: `<${messageLink}|このメッセージ> が <#${message.channel}> で投稿されました。`,
-			});
-		} else {
-			console.log(channelInfo.channel?.name);
-		}
-	}
-});
-
-app.event('channel_created', async ({ event, client, logger }) => {
-	if (event.channel.name?.startsWith('times-')) {
-		logger.debug(event.channel.name);
-		await client.conversations.join({ channel: event.channel.id });
-		logger.info(`Joined channel: ${event.channel.name}`);
-	}
-});
-
-// Lambdaのイベント処理
-// Node.js 24ではcallbackベースのハンドラーが廃止されたため、
-// AwsLambdaReceiverのハンドラーを2引数のasync関数でラップする
-// ref: https://github.com/slackapi/bolt-js/issues/2761
-export const handler = async (
-	event: Record<string, unknown>,
-	context: unknown,
-) => {
-	const boltHandler = await awsLambdaReceiver.start();
-	// boltHandlerは内部的にcallbackを使用しないが、型定義上3引数が必須
-	// biome-ignore lint/suspicious/noExplicitAny: AwsEventの型がexportされていないため
-	return boltHandler(event as any, context, () => {});
-};
diff --git a/infra/lib/times-all-bot-stack.ts b/infra/lib/times-all-bot-stack.ts
index 3ee27c4..47b96c1 100644
--- a/infra/lib/times-all-bot-stack.ts
+++ b/infra/lib/times-all-bot-stack.ts
@@ -6,33 +6,26 @@ import * as iam from 'aws-cdk-lib/aws-iam';
 import * as runtime from 'aws-cdk-lib/aws-lambda';
 import * as lambda from 'aws-cdk-lib/aws-lambda-nodejs';
 import type { Construct } from 'constructs';
+import { loadEnv } from '../../src/env.ts';
 
 export class TimesAllBotStack extends cdk.Stack {
 	constructor(scope: Construct, id: string, props?: cdk.StackProps) {
 		super(scope, id, props);
 
-		const slackBotToken = process.env['SLACK_BOT_TOKEN'];
-		if (!slackBotToken) throw new Error('SLACK_BOT_TOKEN is required');
-		const slackSigningSecret = process.env['SLACK_SIGNING_SECRET'];
-		if (!slackSigningSecret)
-			throw new Error('SLACK_SIGNING_SECRET is required');
-		const timesAllChannelId = process.env['TIMES_ALL_CHANNEL_ID'];
-		if (!timesAllChannelId) throw new Error('TIMES_ALL_CHANNEL_ID is required');
-		const workspaceUrl = process.env['WORKSPACE_URL'];
-		if (!workspaceUrl) throw new Error('WORKSPACE_URL is required');
+		const env = loadEnv();
 
 		const projectRoot = path.join(import.meta.dirname, '../..');
 
 		const fn = new lambda.NodejsFunction(this, 'SlackHandler', {
-			entry: path.join(projectRoot, 'index.ts'),
+			entry: path.join(projectRoot, 'src/handler.ts'),
 			handler: 'handler',
 			runtime: runtime.Runtime.NODEJS_24_X,
 			timeout: cdk.Duration.seconds(30),
 			environment: {
-				SLACK_BOT_TOKEN: slackBotToken,
-				SLACK_SIGNING_SECRET: slackSigningSecret,
-				TIMES_ALL_CHANNEL_ID: timesAllChannelId,
-				WORKSPACE_URL: workspaceUrl,
+				SLACK_BOT_TOKEN: env.slackBotToken,
+				SLACK_SIGNING_SECRET: env.slackSigningSecret,
+				TIMES_ALL_CHANNEL_ID: env.timesAllChannelId,
+				WORKSPACE_URL: env.workspaceUrl,
 			},
 			bundling: {
 				nodeModules: ['@slack/bolt'],
diff --git a/infra/package-lock.json b/infra/package-lock.json
index 9da2a37..56bc11e 100644
--- a/infra/package-lock.json
+++ b/infra/package-lock.json
@@ -9,7 +9,8 @@
 			"version": "1.0.0",
 			"dependencies": {
 				"aws-cdk-lib": "^2.245.0",
-				"constructs": "^10.6.0"
+				"constructs": "^10.6.0",
+				"valibot": "^1.3.1"
 			},
 			"devDependencies": {
 				"@tsconfig/strictest": "^2.0.8",
@@ -984,7 +985,7 @@
 			"version": "6.0.2",
 			"resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.2.tgz",
 			"integrity": "sha512-bGdAIrZ0wiGDo5l8c++HWtbaNCWTS4UTv7RaTH/ThVIgjkveJt83m74bBHMJkuCbslY8ixgLBVZJIOiQlQTjfQ==",
-			"dev": true,
+			"devOptional": true,
 			"license": "Apache-2.0",
 			"bin": {
 				"tsc": "bin/tsc",
@@ -1000,6 +1001,20 @@
 			"integrity": "sha512-AsuCzffGHJybSaRrmr5eHr81mwJU3kjw6M+uprWvCXiNeN9SOGwQ3Jn8jb8m3Z6izVgknn1R0FTCEAP2QrLY/w==",
 			"dev": true,
 			"license": "MIT"
+		},
+		"node_modules/valibot": {
+			"version": "1.3.1",
+			"resolved": "https://registry.npmjs.org/valibot/-/valibot-1.3.1.tgz",
+			"integrity": "sha512-sfdRir/QFM0JaF22hqTroPc5xy4DimuGQVKFrzF1YfGwaS1nJot3Y8VqMdLO2Lg27fMzat2yD3pY5PbAYO39Gg==",
+			"license": "MIT",
+			"peerDependencies": {
+				"typescript": ">=5"
+			},
+			"peerDependenciesMeta": {
+				"typescript": {
+					"optional": true
+				}
+			}
 		}
 	}
 }
diff --git a/infra/package.json b/infra/package.json
index 12f8f0b..9ac596e 100644
--- a/infra/package.json
+++ b/infra/package.json
@@ -11,7 +11,8 @@
 	},
 	"dependencies": {
 		"aws-cdk-lib": "^2.245.0",
-		"constructs": "^10.6.0"
+		"constructs": "^10.6.0",
+		"valibot": "^1.3.1"
 	},
 	"devDependencies": {
 		"@tsconfig/strictest": "^2.0.8",
diff --git a/infra/tsconfig.json b/infra/tsconfig.json
index ed82f00..2989dd3 100644
--- a/infra/tsconfig.json
+++ b/infra/tsconfig.json
@@ -9,5 +9,5 @@
 		"types": ["node"],
 		"resolveJsonModule": true
 	},
-	"include": ["bin/**/*.ts", "lib/**/*.ts"]
+	"include": ["bin/**/*.ts", "lib/**/*.ts", "../src/env.ts"]
 }
diff --git a/joinBotToTimesChannels.ts b/joinBotToTimesChannels.ts
deleted file mode 100644
index 4be8d3a..0000000
--- a/joinBotToTimesChannels.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-import { WebClient } from '@slack/web-api';
-
-const token = process.env['SLACK_BOT_TOKEN']; // .envからBotトークンを取得
-const web = new WebClient(token);
-
-async function joinTimesChannels() {
-	try {
-		// パブリックチャンネルのリストを取得
-		const result = await web.conversations.list({
-			types: 'public_channel',
-			limit: 1000,
-		});
-		const channels = result.channels;
-		console.log(channels?.length); // チャンネルの情報を表示
-		if (!channels) throw new Error('channels is undefined');
-		// `times-` プレフィックスがついたチャンネルにBotを追加
-		for (const channel of channels) {
-			if (channel.name?.startsWith('times-') && channel.is_archived === false) {
-				console.log(channel.name);
-				if (!channel.id) throw new Error('channel id is undefined');
-				await web.conversations.join({ channel: channel.id });
-				console.log(`Joined channel: ${channel.name}`);
-			}
-		}
-	} catch (error) {
-		console.error(error);
-	}
-}
-
-joinTimesChannels();
diff --git a/package-lock.json b/package-lock.json
index 2efeb2e..204eb19 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,7 +9,8 @@
 			"version": "1.0.0",
 			"license": "ISC",
 			"dependencies": {
-				"@slack/bolt": "^4.6.0"
+				"@slack/bolt": "^4.6.0",
+				"valibot": "^1.3.1"
 			},
 			"devDependencies": {
 				"@biomejs/biome": "2.4.9",
@@ -2074,7 +2075,7 @@
 			"version": "6.0.2",
 			"resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.2.tgz",
 			"integrity": "sha512-bGdAIrZ0wiGDo5l8c++HWtbaNCWTS4UTv7RaTH/ThVIgjkveJt83m74bBHMJkuCbslY8ixgLBVZJIOiQlQTjfQ==",
-			"dev": true,
+			"devOptional": true,
 			"license": "Apache-2.0",
 			"bin": {
 				"tsc": "bin/tsc",
@@ -2099,6 +2100,20 @@
 				"node": ">= 0.8"
 			}
 		},
+		"node_modules/valibot": {
+			"version": "1.3.1",
+			"resolved": "https://registry.npmjs.org/valibot/-/valibot-1.3.1.tgz",
+			"integrity": "sha512-sfdRir/QFM0JaF22hqTroPc5xy4DimuGQVKFrzF1YfGwaS1nJot3Y8VqMdLO2Lg27fMzat2yD3pY5PbAYO39Gg==",
+			"license": "MIT",
+			"peerDependencies": {
+				"typescript": ">=5"
+			},
+			"peerDependenciesMeta": {
+				"typescript": {
+					"optional": true
+				}
+			}
+		},
 		"node_modules/vary": {
 			"version": "1.1.2",
 			"resolved": "https://registry.npmjs.org/vary/-/vary-1.1.2.tgz",
diff --git a/package.json b/package.json
index e2dc758..58ea13c 100644
--- a/package.json
+++ b/package.json
@@ -4,17 +4,19 @@
 	"description": "repost times-* channel to \"time-all\"",
 	"type": "module",
 	"scripts": {
-		"dev": "node --env-file=.env index.ts",
+		"dev": "node --env-file=.env src/handler.ts",
 		"lint": "biome check --write .",
 		"format": "biome format .",
 		"check": "biome check .",
-		"typecheck": "tsc --noEmit"
+		"typecheck": "tsc",
+		"test": "node --test 'src/**/*.test.ts'"
 	},
 	"keywords": [],
 	"author": "",
 	"license": "ISC",
 	"dependencies": {
-		"@slack/bolt": "^4.6.0"
+		"@slack/bolt": "^4.6.0",
+		"valibot": "^1.3.1"
 	},
 	"devDependencies": {
 		"@biomejs/biome": "2.4.9",
diff --git a/src/__tests__/env.test.ts b/src/__tests__/env.test.ts
new file mode 100644
index 0000000..68cdb13
--- /dev/null
+++ b/src/__tests__/env.test.ts
@@ -0,0 +1,76 @@
+import assert from 'node:assert/strict';
+import { afterEach, beforeEach, describe, it } from 'node:test';
+import * as v from 'valibot';
+import { loadEnv } from '../env.ts';
+
+describe('loadEnv', () => {
+	const validEnv = {
+		SLACK_SIGNING_SECRET: 'secret',
+		SLACK_BOT_TOKEN: 'xoxb-token',
+		TIMES_ALL_CHANNEL_ID: 'C12345',
+		WORKSPACE_URL: 'https://workspace.slack.com',
+	};
+
+	let originalEnv: NodeJS.ProcessEnv;
+
+	beforeEach(() => {
+		originalEnv = {};
+		for (const key of Object.keys(validEnv)) {
+			originalEnv[key] = process.env[key];
+		}
+		for (const [key, value] of Object.entries(validEnv)) {
+			process.env[key] = value;
+		}
+	});
+
+	afterEach(() => {
+		for (const key of Object.keys(validEnv)) {
+			const original = originalEnv[key];
+			if (original === undefined) {
+				delete process.env[key];
+			} else {
+				process.env[key] = original;
+			}
+		}
+	});
+
+	it('すべての環境変数が設定されている場合はEnvオブジェクトを返す', () => {
+		const env = loadEnv();
+		assert.deepEqual(env, {
+			slackSigningSecret: 'secret',
+			slackBotToken: 'xoxb-token',
+			timesAllChannelId: 'C12345',
+			workspaceUrl: 'https://workspace.slack.com',
+		});
+	});
+
+	it('SLACK_SIGNING_SECRETが未設定の場合はValiErrorを投げる', () => {
+		delete process.env['SLACK_SIGNING_SECRET'];
+		assert.throws(() => loadEnv(), v.ValiError);
+	});
+
+	it('SLACK_BOT_TOKENが未設定の場合はValiErrorを投げる', () => {
+		delete process.env['SLACK_BOT_TOKEN'];
+		assert.throws(() => loadEnv(), v.ValiError);
+	});
+
+	it('TIMES_ALL_CHANNEL_IDが未設定の場合はValiErrorを投げる', () => {
+		delete process.env['TIMES_ALL_CHANNEL_ID'];
+		assert.throws(() => loadEnv(), v.ValiError);
+	});
+
+	it('WORKSPACE_URLが未設定の場合はValiErrorを投げる', () => {
+		delete process.env['WORKSPACE_URL'];
+		assert.throws(() => loadEnv(), v.ValiError);
+	});
+
+	it('WORKSPACE_URLが不正なURLの場合はValiErrorを投げる', () => {
+		process.env['WORKSPACE_URL'] = 'not-a-url';
+		assert.throws(() => loadEnv(), v.ValiError);
+	});
+
+	it('WORKSPACE_URLが末尾スラッシュを含む場合はValiErrorを投げる', () => {
+		process.env['WORKSPACE_URL'] = 'https://workspace.slack.com/';
+		assert.throws(() => loadEnv(), v.ValiError);
+	});
+});
diff --git a/src/app.ts b/src/app.ts
new file mode 100644
index 0000000..8859e9c
--- /dev/null
+++ b/src/app.ts
@@ -0,0 +1,25 @@
+import { App, AwsLambdaReceiver } from '@slack/bolt';
+import type { Env } from './env.ts';
+import { handleChannelCreated } from './handlers/channelCreated.ts';
+import { createMessageHandler } from './handlers/message.ts';
+
+export interface SlackApp {
+	app: App;
+	receiver: AwsLambdaReceiver;
+}
+
+export function createSlackApp(env: Env): SlackApp {
+	const receiver = new AwsLambdaReceiver({
+		signingSecret: env.slackSigningSecret,
+	});
+
+	const app = new App({
+		token: env.slackBotToken,
+		receiver,
+	});
+
+	app.message(createMessageHandler(env.timesAllChannelId, env.workspaceUrl));
+	app.event('channel_created', handleChannelCreated);
+
+	return { app, receiver };
+}
diff --git a/src/env.ts b/src/env.ts
new file mode 100644
index 0000000..3bdc38d
--- /dev/null
+++ b/src/env.ts
@@ -0,0 +1,35 @@
+import * as v from 'valibot';
+
+const EnvSchema = v.object({
+	SLACK_SIGNING_SECRET: v.pipe(v.string(), v.nonEmpty()),
+	SLACK_BOT_TOKEN: v.pipe(v.string(), v.nonEmpty()),
+	TIMES_ALL_CHANNEL_ID: v.pipe(v.string(), v.nonEmpty()),
+	WORKSPACE_URL: v.pipe(
+		v.string(),
+		v.url(),
+		v.check((s) => !s.endsWith('/'), 'URL must not end with a trailing slash'),
+	),
+});
+
+export type Env = {
+	slackSigningSecret: string;
+	slackBotToken: string;
+	timesAllChannelId: string;
+	workspaceUrl: string;
+};
+
+export function loadEnv(): Env {
+	const parsed = v.parse(EnvSchema, {
+		SLACK_SIGNING_SECRET: process.env['SLACK_SIGNING_SECRET'],
+		SLACK_BOT_TOKEN: process.env['SLACK_BOT_TOKEN'],
+		TIMES_ALL_CHANNEL_ID: process.env['TIMES_ALL_CHANNEL_ID'],
+		WORKSPACE_URL: process.env['WORKSPACE_URL'],
+	});
+
+	return {
+		slackSigningSecret: parsed.SLACK_SIGNING_SECRET,
+		slackBotToken: parsed.SLACK_BOT_TOKEN,
+		timesAllChannelId: parsed.TIMES_ALL_CHANNEL_ID,
+		workspaceUrl: parsed.WORKSPACE_URL,
+	};
+}
diff --git a/src/handler.ts b/src/handler.ts
new file mode 100644
index 0000000..a893b28
--- /dev/null
+++ b/src/handler.ts
@@ -0,0 +1,19 @@
+import { createSlackApp } from './app.ts';
+import { loadEnv } from './env.ts';
+
+const env = loadEnv();
+const { receiver } = createSlackApp(env);
+
+// Lambdaのイベント処理
+// Node.js 24ではcallbackベースのハンドラーが廃止されたため、
+// AwsLambdaReceiverのハンドラーを2引数のasync関数でラップする
+// ref: https://github.com/slackapi/bolt-js/issues/2761
+export const handler = async (
+	event: Record<string, unknown>,
+	context: unknown,
+) => {
+	const boltHandler = await receiver.start();
+	// boltHandlerは内部的にcallbackを使用しないが、型定義上3引数が必須
+	// biome-ignore lint/suspicious/noExplicitAny: AwsEventの型がexportされていないため
+	return boltHandler(event as any, context, () => {});
+};
diff --git a/src/handlers/__tests__/channelCreated.test.ts b/src/handlers/__tests__/channelCreated.test.ts
new file mode 100644
index 0000000..fadd404
--- /dev/null
+++ b/src/handlers/__tests__/channelCreated.test.ts
@@ -0,0 +1,42 @@
+import assert from 'node:assert/strict';
+import { describe, it, mock } from 'node:test';
+import { handleChannelCreated } from '../channelCreated.ts';
+
+describe('handleChannelCreated', () => {
+	function makeArgs(channelName: string, channelId: string) {
+		return {
+			event: {
+				channel: { name: channelName, id: channelId },
+			},
+			client: {
+				conversations: {
+					join: mock.fn(() => Promise.resolve()),
+				},
+			},
+			logger: {
+				debug: mock.fn(),
+				info: mock.fn(),
+			},
+		};
+	}
+
+	it('times-で始まるチャンネルにjoinする', async () => {
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args = makeArgs('times-yamada', 'C12345') as any;
+		await handleChannelCreated(args);
+
+		assert.equal(args.client.conversations.join.mock.callCount(), 1);
+		assert.deepEqual(
+			args.client.conversations.join.mock.calls[0].arguments[0],
+			{ channel: 'C12345' },
+		);
+	});
+
+	it('times-以外のチャンネルにはjoinしない', async () => {
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args = makeArgs('general', 'C12345') as any;
+		await handleChannelCreated(args);
+
+		assert.equal(args.client.conversations.join.mock.callCount(), 0);
+	});
+});
diff --git a/src/handlers/__tests__/message.test.ts b/src/handlers/__tests__/message.test.ts
new file mode 100644
index 0000000..56606c2
--- /dev/null
+++ b/src/handlers/__tests__/message.test.ts
@@ -0,0 +1,105 @@
+import assert from 'node:assert/strict';
+import { describe, it, mock } from 'node:test';
+import { createMessageHandler } from '../message.ts';
+
+describe('createMessageHandler', () => {
+	const timesAllChannelId = 'C_TIMES_ALL';
+	const workspaceUrl = 'https://workspace.slack.com';
+	const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
+
+	function makeArgs(
+		message: Record<string, unknown>,
+		channelName: string | undefined = 'times-yamada',
+	) {
+		return {
+			message,
+			client: {
+				conversations: {
+					info: mock.fn(() =>
+						Promise.resolve({
+							channel: { name: channelName },
+						}),
+					),
+				},
+				chat: {
+					postMessage: mock.fn(() => Promise.resolve()),
+				},
+			},
+		};
+	}
+
+	it('timesチャンネルのメッセージをtimes-allに転送する', async () => {
+		const message = {
+			type: 'message',
+			subtype: undefined,
+			channel: 'C_TIMES_YAMADA',
+			channel_type: 'channel',
+			text: 'hello',
+			ts: '1234567890.123456',
+			user: 'U12345',
+		};
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args = makeArgs(message) as any;
+		await handler(args);
+
+		assert.equal(args.client.chat.postMessage.mock.callCount(), 1);
+		const call = args.client.chat.postMessage.mock.calls[0];
+		assert.equal(call.arguments[0].channel, timesAllChannelId);
+		assert.ok(
+			(call.arguments[0].text as string).includes(
+				'https://workspace.slack.com/archives/C_TIMES_YAMADA/p1234567890123456',
+			),
+		);
+	});
+
+	it('times-以外のチャンネルは転送しない', async () => {
+		const message = {
+			type: 'message',
+			subtype: undefined,
+			channel: 'C_GENERAL',
+			channel_type: 'channel',
+			text: 'hello',
+			ts: '1234567890.123456',
+			user: 'U12345',
+		};
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args = makeArgs(message, 'general') as any;
+		await handler(args);
+
+		assert.equal(args.client.chat.postMessage.mock.callCount(), 0);
+	});
+
+	it('subtypeを持つメッセージは転送しない', async () => {
+		const message = {
+			type: 'message',
+			subtype: 'channel_join',
+			channel: 'C_TIMES_YAMADA',
+			channel_type: 'channel',
+			ts: '1234567890.123456',
+		};
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args = makeArgs(message) as any;
+		await handler(args);
+
+		assert.equal(args.client.conversations.info.mock.callCount(), 0);
+		assert.equal(args.client.chat.postMessage.mock.callCount(), 0);
+	});
+
+	it('DMメッセージは転送しない', async () => {
+		const message = {
+			type: 'message',
+			subtype: undefined,
+			channel: 'C_TIMES_YAMADA',
+			channel_type: 'im',
+			text: 'hello',
+			ts: '1234567890.123456',
+			user: 'U12345',
+		};
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args = makeArgs(message) as any;
+		await handler(args);
+
+		assert.equal(args.client.conversations.info.mock.callCount(), 0);
+		assert.equal(args.client.chat.postMessage.mock.callCount(), 0);
+	});
+});
diff --git a/src/handlers/channelCreated.ts b/src/handlers/channelCreated.ts
new file mode 100644
index 0000000..ea15fea
--- /dev/null
+++ b/src/handlers/channelCreated.ts
@@ -0,0 +1,16 @@
+import type { AllMiddlewareArgs, SlackEventMiddlewareArgs } from '@slack/bolt';
+import { isTimesChannel } from '../lib/timesChannel.ts';
+
+export async function handleChannelCreated({
+	event,
+	client,
+	logger,
+}: AllMiddlewareArgs & SlackEventMiddlewareArgs<'channel_created'>) {
+	const { name, id } = event.channel;
+	if (!name || !isTimesChannel(name)) {
+		return;
+	}
+	logger.debug(name);
+	await client.conversations.join({ channel: id });
+	logger.info(`Joined channel: ${name}`);
+}
diff --git a/src/handlers/message.ts b/src/handlers/message.ts
new file mode 100644
index 0000000..7470ce7
--- /dev/null
+++ b/src/handlers/message.ts
@@ -0,0 +1,42 @@
+import type { AllMiddlewareArgs, SlackEventMiddlewareArgs } from '@slack/bolt';
+import { buildForwardText } from '../lib/forwardText.ts';
+import { isForwardableMessage } from '../lib/messageFilter.ts';
+import { buildMessageLink } from '../lib/messageLink.ts';
+import { isTimesChannel } from '../lib/timesChannel.ts';
+
+export function createMessageHandler(
+	timesAllChannelId: string,
+	workspaceUrl: string,
+) {
+	return async ({
+		message,
+		client,
+	}: AllMiddlewareArgs & SlackEventMiddlewareArgs<'message'>) => {
+		console.log('received message');
+		if (!isForwardableMessage(message, timesAllChannelId)) {
+			return;
+		}
+
+		const channelInfo = await client.conversations.info({
+			channel: message.channel,
+		});
+		const channelName = channelInfo.channel?.name;
+		if (!channelName || !isTimesChannel(channelName)) {
+			console.log(channelName);
+			return;
+		}
+
+		console.log('channel name starts with times-');
+		const messageLink = buildMessageLink(
+			workspaceUrl,
+			message.channel,
+			message.ts,
+		);
+		console.log('messageLink:', messageLink);
+		const text = buildForwardText(messageLink, message.channel);
+		await client.chat.postMessage({
+			channel: timesAllChannelId,
+			text,
+		});
+	};
+}
diff --git a/src/joinBotToTimesChannels.ts b/src/joinBotToTimesChannels.ts
new file mode 100644
index 0000000..9043547
--- /dev/null
+++ b/src/joinBotToTimesChannels.ts
@@ -0,0 +1,47 @@
+import { WebClient } from '@slack/web-api';
+import { isTimesChannel } from './lib/timesChannel.ts';
+
+const token = process.env['SLACK_BOT_TOKEN'];
+if (!token) throw new Error('SLACK_BOT_TOKEN is undefined');
+const web = new WebClient(token);
+
+async function joinTimesChannels() {
+	let cursor: string | undefined;
+
+	do {
+		const result = await web.conversations.list({
+			types: 'public_channel',
+			limit: 1000,
+			...(cursor ? { cursor } : {}),
+		});
+		if (!result.ok) {
+			throw new Error(
+				`Failed to list conversations: ${result.error ?? 'unknown error'}`,
+			);
+		}
+		const channels = result.channels;
+		if (!channels) {
+			throw new Error('channels is undefined in conversations.list response');
+		}
+		if (channels.length === 0) break;
+
+		console.log(`fetched ${channels.length} channels`);
+
+		for (const channel of channels) {
+			if (
+				channel.name &&
+				isTimesChannel(channel.name) &&
+				channel.is_archived === false
+			) {
+				console.log(channel.name);
+				if (!channel.id) throw new Error('channel id is undefined');
+				await web.conversations.join({ channel: channel.id });
+				console.log(`Joined channel: ${channel.name}`);
+			}
+		}
+
+		cursor = result.response_metadata?.next_cursor || undefined;
+	} while (cursor);
+}
+
+await joinTimesChannels();
diff --git a/src/lib/__tests__/forwardText.test.ts b/src/lib/__tests__/forwardText.test.ts
new file mode 100644
index 0000000..dca9325
--- /dev/null
+++ b/src/lib/__tests__/forwardText.test.ts
@@ -0,0 +1,16 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { buildForwardText } from '../forwardText.ts';
+
+describe('buildForwardText', () => {
+	it('Slackのメッセージリンクとチャンネルメンションを含むテキストを構築する', () => {
+		const result = buildForwardText(
+			'https://workspace.slack.com/archives/C12345/p1234567890123456',
+			'C12345',
+		);
+		assert.equal(
+			result,
+			'<https://workspace.slack.com/archives/C12345/p1234567890123456|このメッセージ> が <#C12345> で投稿されました。',
+		);
+	});
+});
diff --git a/src/lib/__tests__/messageFilter.test.ts b/src/lib/__tests__/messageFilter.test.ts
new file mode 100644
index 0000000..8ff12f9
--- /dev/null
+++ b/src/lib/__tests__/messageFilter.test.ts
@@ -0,0 +1,66 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import type { AllMessageEvents, GenericMessageEvent } from '@slack/types';
+import { isForwardableMessage } from '../messageFilter.ts';
+
+describe('isForwardableMessage', () => {
+	const timesAllChannelId = 'C_TIMES_ALL';
+
+	const baseMessage: GenericMessageEvent = {
+		type: 'message',
+		subtype: undefined,
+		channel: 'C_OTHER',
+		channel_type: 'channel',
+		text: 'hello',
+		ts: '1234567890.123456',
+		user: 'U12345',
+	} as GenericMessageEvent;
+
+	it('通常のチャンネルメッセージはtrueを返す', () => {
+		assert.equal(isForwardableMessage(baseMessage, timesAllChannelId), true);
+	});
+
+	it('times-allチャンネルのメッセージはfalseを返す', () => {
+		const message = { ...baseMessage, channel: timesAllChannelId };
+		assert.equal(isForwardableMessage(message, timesAllChannelId), false);
+	});
+
+	it('DMメッセージはfalseを返す', () => {
+		const message = { ...baseMessage, channel_type: 'im' as const };
+		assert.equal(isForwardableMessage(message, timesAllChannelId), false);
+	});
+
+	it('subtypeを持つメッセージはfalseを返す (channel_join)', () => {
+		const message = {
+			type: 'message',
+			subtype: 'channel_join',
+			channel: 'C_OTHER',
+			channel_type: 'channel',
+			ts: '1234567890.123456',
+		} as AllMessageEvents;
+		assert.equal(isForwardableMessage(message, timesAllChannelId), false);
+	});
+
+	it('subtypeを持つメッセージはfalseを返す (bot_message)', () => {
+		const message = {
+			type: 'message',
+			subtype: 'bot_message',
+			channel: 'C_OTHER',
+			channel_type: 'channel',
+			ts: '1234567890.123456',
+		} as AllMessageEvents;
+		assert.equal(isForwardableMessage(message, timesAllChannelId), false);
+	});
+
+	it('subtypeを持つメッセージはfalseを返す (message_changed)', () => {
+		const message = {
+			type: 'message',
+			subtype: 'message_changed',
+			channel: 'C_OTHER',
+			channel_type: 'channel',
+			ts: '1234567890.123456',
+			hidden: true,
+		} as AllMessageEvents;
+		assert.equal(isForwardableMessage(message, timesAllChannelId), false);
+	});
+});
diff --git a/src/lib/__tests__/messageLink.test.ts b/src/lib/__tests__/messageLink.test.ts
new file mode 100644
index 0000000..f6fb2a8
--- /dev/null
+++ b/src/lib/__tests__/messageLink.test.ts
@@ -0,0 +1,29 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { buildMessageLink } from '../messageLink.ts';
+
+describe('buildMessageLink', () => {
+	it('タイムスタンプのドットを除去してSlackのメッセージリンクを構築する', () => {
+		const result = buildMessageLink(
+			'https://workspace.slack.com',
+			'C12345',
+			'1234567890.123456',
+		);
+		assert.equal(
+			result,
+			'https://workspace.slack.com/archives/C12345/p1234567890123456',
+		);
+	});
+
+	it('ドットのないタイムスタンプでも動作する', () => {
+		const result = buildMessageLink(
+			'https://workspace.slack.com',
+			'C12345',
+			'1234567890123456',
+		);
+		assert.equal(
+			result,
+			'https://workspace.slack.com/archives/C12345/p1234567890123456',
+		);
+	});
+});
diff --git a/src/lib/__tests__/timesChannel.test.ts b/src/lib/__tests__/timesChannel.test.ts
new file mode 100644
index 0000000..a3654cd
--- /dev/null
+++ b/src/lib/__tests__/timesChannel.test.ts
@@ -0,0 +1,25 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { isTimesChannel } from '../timesChannel.ts';
+
+describe('isTimesChannel', () => {
+	it('times-で始まるチャンネル名にtrueを返す', () => {
+		assert.equal(isTimesChannel('times-yamada'), true);
+	});
+
+	it('times-のみでもtrueを返す', () => {
+		assert.equal(isTimesChannel('times-'), true);
+	});
+
+	it('times-で始まらないチャンネル名にfalseを返す', () => {
+		assert.equal(isTimesChannel('general'), false);
+	});
+
+	it('timesだけではfalseを返す', () => {
+		assert.equal(isTimesChannel('times'), false);
+	});
+
+	it('空文字にfalseを返す', () => {
+		assert.equal(isTimesChannel(''), false);
+	});
+});
diff --git a/src/lib/forwardText.ts b/src/lib/forwardText.ts
new file mode 100644
index 0000000..6247247
--- /dev/null
+++ b/src/lib/forwardText.ts
@@ -0,0 +1,6 @@
+export function buildForwardText(
+	messageLink: string,
+	channelId: string,
+): string {
+	return `<${messageLink}|このメッセージ> が <#${channelId}> で投稿されました。`;
+}
diff --git a/src/lib/messageFilter.ts b/src/lib/messageFilter.ts
new file mode 100644
index 0000000..a8b2741
--- /dev/null
+++ b/src/lib/messageFilter.ts
@@ -0,0 +1,16 @@
+import type { AllMessageEvents } from '@slack/types';
+
+/**
+ * 転送対象のメッセージかどうかを判定する。
+ * subtypeを持つメッセージ(channel_join, message_changed, bot_message等)は
+ * すべて転送対象外とする。hidden判定も不要(hidden: trueを持つのはsubtype付きのみ)。
+ */
+export function isForwardableMessage(
+	message: AllMessageEvents,
+	timesAllChannelId: string,
+): boolean {
+	if (message.subtype !== undefined) return false;
+	if (message.channel_type !== 'channel') return false;
+	if (message.channel === timesAllChannelId) return false;
+	return true;
+}
diff --git a/src/lib/messageLink.ts b/src/lib/messageLink.ts
new file mode 100644
index 0000000..80c602e
--- /dev/null
+++ b/src/lib/messageLink.ts
@@ -0,0 +1,8 @@
+export function buildMessageLink(
+	workspaceUrl: string,
+	channelId: string,
+	ts: string,
+): string {
+	const timestamp = ts.replace('.', '');
+	return `${workspaceUrl}/archives/${channelId}/p${timestamp}`;
+}
diff --git a/src/lib/timesChannel.ts b/src/lib/timesChannel.ts
new file mode 100644
index 0000000..37a0c77
--- /dev/null
+++ b/src/lib/timesChannel.ts
@@ -0,0 +1,5 @@
+const TIMES_PREFIX = 'times-';
+
+export function isTimesChannel(name: string): boolean {
+	return name.startsWith(TIMES_PREFIX);
+}
diff --git a/tsconfig.json b/tsconfig.json
index d05d7b6..fb672c4 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -3,7 +3,9 @@
 	"compilerOptions": {
 		"target": "es2022",
 		"module": "node16",
-		"types": ["node"]
+		"types": ["node"],
+		"allowImportingTsExtensions": true,
+		"noEmit": true
 	},
 	"exclude": ["infra"]
 }