diff --git a/frontend/src/pages/NotFound.tsx b/frontend/src/pages/NotFound.tsx
index cefa2c9..a1b7f2f 100644
--- a/frontend/src/pages/NotFound.tsx
+++ b/frontend/src/pages/NotFound.tsx
@@ -10,5 +10,9 @@ export default () => (
         <meta name="robots" content="noindex" />
         <title>ページないよ (笑) | {SITE_TITLE}</title>
       </Helmet>
-      Not Found
+      <div className="text-6xl font-bold italic text-transparent whitespace-nowrap
+                   bg-[linear-gradient(90deg,#ff0000,#ff8800,#ffff00,#00ff00,#00ffff,#0000ff,#ff00ff,#ff0000)]
+                   bg-clip-text bg-[length:200%_100%] animate-rainbow-scroll drop-shadow-[0_0_6px_white]">
+        404<br />ページないよ（笑）
+      </div>
     </MainArea>)
diff --git a/frontend/tailwind.config.js b/frontend/tailwind.config.js
index b7d6d02..a813597 100644
--- a/frontend/tailwind.config.js
+++ b/frontend/tailwind.config.js
@@ -5,7 +5,17 @@ export default {
   content: ['./index.html',
             './src/**/*.{js,ts,jsx,tsx}'],
   theme: {
-    extend: {},
+    extend: {
+      keyframes: {
+        'rainbow-scroll': {
+          '0%': { backgroundPosition: '0% 50%' },
+          '100%': { backgroundPosition: '200% 50%' },
+        },
+      },
+      animation: {
+        'rainbow-scroll': 'rainbow-scroll .25s linear infinite',
+      },
+    }
   },
   plugins: [],
 } satisfies Config