diff --git a/index.js b/index.js
index b307d27f..a6ce2532 100644
--- a/index.js
+++ b/index.js
@@ -2,9 +2,14 @@
 const http = require('http');
 const server = http.createServer((req, res) => {
   res.writeHead(200, {
-    'Content-Type': 'text/plain; charset=utf-8'
+    'Content-Type': 'text/html; charset=utf-8'
   });
-  res.write(req.headers['user-agent']);
+  res.write(`<!DOCTYPE html>
+  <html lang="ja">
+    <body>
+      <h1>HTMLの一番大きい見出しを表示します</h1>
+    </body>
+  </html>`);
   res.end();
 });
 const port = 8000;
