diff --git a/posimai-dev/server.js b/posimai-dev/server.js
index 81a0bffa..c58b51e2 100644
--- a/posimai-dev/server.js
+++ b/posimai-dev/server.js
@@ -3,14 +3,30 @@ const express = require('express');
 const { WebSocketServer } = require('ws');
 const pty = require('node-pty');
 const http = require('http');
+const https = require('https');
+const fs = require('fs');
 const path = require('path');
+const os = require('os');
 
 const app = express();
 const PORT = process.env.PORT || 3333;
 
 app.use(express.static(path.join(__dirname)));
 
-const server = http.createServer(app);
+// ホームディレクトリのTailscale証明書を自動検出
+function findCert() {
+  const home = os.homedir();
+  const crt = fs.readdirSync(home).find((f) => f.endsWith('.crt'));
+  if (!crt) return null;
+  const key = crt.replace('.crt', '.key');
+  if (!fs.existsSync(path.join(home, key))) return null;
+  return { cert: fs.readFileSync(path.join(home, crt)), key: fs.readFileSync(path.join(home, key)) };
+}
+
+const tlsOpts = findCert();
+const server = tlsOpts ? https.createServer(tlsOpts, app) : http.createServer(app);
+const proto = tlsOpts ? 'https' : 'http';
+
 const wss = new WebSocketServer({ server, path: '/terminal' });
 
 wss.on('connection', (ws) => {
@@ -42,5 +58,5 @@ wss.on('connection', (ws) => {
 });
 
 server.listen(PORT, '0.0.0.0', () => {
-  console.log(`posimai-dev running on http://0.0.0.0:${PORT}`);
+  console.log(`posimai-dev running on ${proto}://0.0.0.0:${PORT}`);
 });