diff --git a/__tests__/wait.test.ts b/__tests__/wait.test.ts
deleted file mode 100644
index 1336aaa..0000000
--- a/__tests__/wait.test.ts
+++ /dev/null
@@ -1,25 +0,0 @@
-/**
- * Unit tests for src/wait.ts
- */
-
-import { wait } from '../src/wait'
-import { expect } from '@jest/globals'
-
-describe('wait.ts', () => {
-  it('throws an invalid number', async () => {
-    const input = parseInt('foo', 10)
-    expect(isNaN(input)).toBe(true)
-
-    await expect(wait(input)).rejects.toThrow('milliseconds not a number')
-  })
-
-  it('waits with a valid number', async () => {
-    const start = new Date()
-    await wait(500)
-    const end = new Date()
-
-    const delta = Math.abs(end.getTime() - start.getTime())
-
-    expect(delta).toBeGreaterThan(450)
-  })
-})
diff --git a/action.yml b/action.yml
index 101186a..9f13ad0 100644
--- a/action.yml
+++ b/action.yml
@@ -1,11 +1,7 @@
-name: 'The name of your action here'
-description: 'Provide a description here'
-author: 'Your name or organization here'
-
-# Add your action's branding here. This will appear on the GitHub Marketplace.
-branding:
-  icon: 'heart'
-  color: 'red'
+name: 'GitHub notice to Slack'
+description:
+  'This workflow is triggered by the opening of a pull request and notifies
+  users assigned as reviewers via mention on Slack.'
 
 # Define your inputs here.
 inputs:
diff --git a/src/create-context.ts b/src/create-context.ts
new file mode 100644
index 0000000..cb39f21
--- /dev/null
+++ b/src/create-context.ts
@@ -0,0 +1,47 @@
+import { PullRequestEvent } from '@octokit/webhooks-types'
+import { toSlackUser } from './to-slack-user'
+
+interface ImageElement {
+  type: 'image'
+  image_url: string
+  alt_text: string
+}
+
+interface TextElement {
+  type: 'mrkdwn'
+  text: string
+}
+
+export interface Context {
+  type: 'context'
+  elements: (ImageElement | TextElement)[]
+}
+
+// createContextはFooterみたいなやつで、PR作成者とそのレポジトリ名が表示されるようになっている
+export function createContext(payload: PullRequestEvent): Context {
+  const {
+    pull_request: { user },
+    repository: { full_name }
+  } = payload
+
+  const creator = toSlackUser(user.login)
+
+  const contextText = `${creator} - :github: ${full_name}`
+
+  const context: Context = {
+    type: 'context',
+    elements: [
+      {
+        type: 'image',
+        image_url: user.avatar_url,
+        alt_text: user.login
+      },
+      {
+        type: 'mrkdwn',
+        text: contextText
+      }
+    ]
+  }
+
+  return context
+}
diff --git a/src/create-section.ts b/src/create-section.ts
new file mode 100644
index 0000000..84a0e19
--- /dev/null
+++ b/src/create-section.ts
@@ -0,0 +1,31 @@
+import { PullRequestEvent } from '@octokit/webhooks-types'
+import { toSlackUsers } from './to-slack-users'
+
+export interface Section {
+  type: 'section'
+  text: {
+    type: 'mrkdwn'
+    text: string
+  }
+}
+
+// createSectionでメッセージの本文を作成。レビューアーの一覧とPRタイトルのリンクが表示される。
+// toSlackUsersは Record<GithubAccountName, SlackAccountName> をハードコードで管理していて、Githubのアカウント名からSlackのメンションを作成している
+export function createSection(payload: PullRequestEvent): Section {
+  const {
+    pull_request: { title, html_url, number, requested_reviewers }
+  } = payload
+
+  const reviewers = toSlackUsers(requested_reviewers)
+
+  const sectionText = `${reviewers.join(' ')}\n*<${html_url}|#${number} - ${title}>*`
+  const section: Section = {
+    type: 'section',
+    text: {
+      type: 'mrkdwn',
+      text: sectionText
+    }
+  }
+
+  return section
+}
diff --git a/src/create-slack-message.ts b/src/create-slack-message.ts
new file mode 100644
index 0000000..c7263d2
--- /dev/null
+++ b/src/create-slack-message.ts
@@ -0,0 +1,26 @@
+import * as core from '@actions/core'
+import * as github from '@actions/github'
+import { PullRequestEvent } from '@octokit/webhooks-types'
+import { createContext } from './create-context'
+import { createSection } from './create-section'
+
+export function createSlackMessage(): void {
+  const payload = github.context.payload as PullRequestEvent
+
+  if (payload.action !== 'opened') {
+    throw new Error(
+      'This action is supposed to be run on pull_request opened event'
+    )
+  }
+
+  if (!payload.pull_request) {
+    throw new Error('This action is supposed to be run on pull_request event')
+  }
+
+  const section = createSection(payload)
+  const context = createContext(payload)
+
+  const message = JSON.stringify({ blocks: [section, context] })
+
+  core.setOutput('message', message)
+}
diff --git a/src/main.ts b/src/main.ts
index c804f90..68a0331 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,5 +1,5 @@
 import * as core from '@actions/core'
-import { wait } from './wait'
+import { createSlackMessage } from './create-slack-message'
 
 /**
  * The main function for the action.
@@ -7,18 +7,7 @@ import { wait } from './wait'
  */
 export async function run(): Promise<void> {
   try {
-    const ms: string = core.getInput('milliseconds')
-
-    // Debug logs are only output if the `ACTIONS_STEP_DEBUG` secret is true
-    core.debug(`Waiting ${ms} milliseconds ...`)
-
-    // Log the current timestamp, wait, then log the new timestamp
-    core.debug(new Date().toTimeString())
-    await wait(parseInt(ms, 10))
-    core.debug(new Date().toTimeString())
-
-    // Set outputs for other workflow steps to use
-    core.setOutput('time', new Date().toTimeString())
+    createSlackMessage()
   } catch (error) {
     // Fail the workflow run if an error occurs
     if (error instanceof Error) core.setFailed(error.message)
diff --git a/src/to-slack-user.ts b/src/to-slack-user.ts
new file mode 100644
index 0000000..8bbb309
--- /dev/null
+++ b/src/to-slack-user.ts
@@ -0,0 +1,8 @@
+export function toSlackUser(githubUsername: string): string {
+  const userMappings: Record<string, string> = {
+    rysiva: 'Ryohei'
+  }
+
+  const slackUsername = userMappings[githubUsername]
+  return slackUsername ? `<@${slackUsername}>` : githubUsername
+}
diff --git a/src/to-slack-users.ts b/src/to-slack-users.ts
new file mode 100644
index 0000000..86d957a
--- /dev/null
+++ b/src/to-slack-users.ts
@@ -0,0 +1,11 @@
+import { User, Team } from '@octokit/webhooks-types'
+import { toSlackUser } from './to-slack-user'
+
+export function toSlackUsers(requestedReviewers: (User | Team)[]): string[] {
+  return requestedReviewers.map(reviewer => {
+    if ('login' in reviewer) {
+      return toSlackUser(reviewer.login)
+    }
+    throw new Error('ログインプロパティが見つかりません')
+  })
+}
diff --git a/src/wait.ts b/src/wait.ts
deleted file mode 100644
index 0ddf692..0000000
--- a/src/wait.ts
+++ /dev/null
@@ -1,14 +0,0 @@
-/**
- * Wait for a number of milliseconds.
- * @param milliseconds The number of milliseconds to wait.
- * @returns {Promise<string>} Resolves with 'done!' after the wait is over.
- */
-export async function wait(milliseconds: number): Promise<string> {
-  return new Promise(resolve => {
-    if (isNaN(milliseconds)) {
-      throw new Error('milliseconds not a number')
-    }
-
-    setTimeout(() => resolve('done!'), milliseconds)
-  })
-}