diff --git a/src/webviewContent.ts b/src/webviewContent.ts
index 63440ff..d13d356 100644
--- a/src/webviewContent.ts
+++ b/src/webviewContent.ts
@@ -6,8 +6,8 @@ export function getWebviewContent(imageSrc: string): string {
       <meta charset="UTF-8">
       <title>ImageMarkPengent</title>
       <style>
-        body { margin: 0; padding: 0; }
-        canvas { display: block; }
+        html, body { height: 100%; margin: 0; padding: 0; overflow: hidden; }
+        #canvas { display: block; width: 100vw; height: 100vh; background: #222; cursor: grab; }
       </style>
     </head>
     <body>
@@ -15,13 +15,90 @@ export function getWebviewContent(imageSrc: string): string {
       <script>
       const canvas = document.getElementById('canvas');
       const ctx = canvas.getContext('2d');
-      const img = new Image();
+      let img = new Image();
       img.src = "${imageSrc}";
+
+      // ズーム・パン用変数
+      let scale = 1;
+      let minScale = 0.1;
+      let maxScale = 10;
+      let offsetX = 0;
+      let offsetY = 0;
+      let isDragging = false;
+      let dragStartX = 0;
+      let dragStartY = 0;
+      let lastOffsetX = 0;
+      let lastOffsetY = 0;
+
+      // リサイズ対応
+      function resizeCanvas() {
+        canvas.width = window.innerWidth;
+        canvas.height = window.innerHeight;
+        draw();
+      }
+      window.addEventListener('resize', resizeCanvas);
+
+      // 画像ロード後、初期ズーム・位置を計算
       img.onload = () => {
-        canvas.width = img.width;
-        canvas.height = img.height;
-        ctx.drawImage(img, 0, 0);
+        // 画像全体がcanvasに収まるように初期scaleを計算
+        const scaleX = canvas.width / img.width;
+        const scaleY = canvas.height / img.height;
+        scale = Math.min(scaleX, scaleY, 1);
+        // 画像が中央に来るように初期オフセット
+        offsetX = (canvas.width - img.width * scale) / 2;
+        offsetY = (canvas.height - img.height * scale) / 2;
+        draw();
       };
+
+      // 描画関数
+      function draw() {
+        ctx.clearRect(0, 0, canvas.width, canvas.height);
+        ctx.save();
+        ctx.setTransform(scale, 0, 0, scale, offsetX, offsetY);
+        ctx.drawImage(img, 0, 0);
+        ctx.restore();
+      }
+
+      // ホイールでズーム
+      canvas.addEventListener('wheel', (e) => {
+        e.preventDefault();
+        const mouseX = e.offsetX;
+        const mouseY = e.offsetY;
+        const prevScale = scale;
+        if (e.deltaY < 0) {
+          scale *= 1.1;
+        } else {
+          scale /= 1.1;
+        }
+        scale = Math.max(minScale, Math.min(maxScale, scale));
+        // ズーム位置をマウス座標中心に
+        offsetX = mouseX - ((mouseX - offsetX) * (scale / prevScale));
+        offsetY = mouseY - ((mouseY - offsetY) * (scale / prevScale));
+        draw();
+      }, { passive: false });
+
+      // ドラッグでパン
+      canvas.addEventListener('mousedown', (e) => {
+        isDragging = true;
+        dragStartX = e.clientX;
+        dragStartY = e.clientY;
+        lastOffsetX = offsetX;
+        lastOffsetY = offsetY;
+        canvas.style.cursor = 'grabbing';
+      });
+      window.addEventListener('mousemove', (e) => {
+        if (!isDragging) return;
+        offsetX = lastOffsetX + (e.clientX - dragStartX);
+        offsetY = lastOffsetY + (e.clientY - dragStartY);
+        draw();
+      });
+      window.addEventListener('mouseup', () => {
+        isDragging = false;
+        canvas.style.cursor = 'grab';
+      });
+
+      // 初期リサイズ
+      resizeCanvas();
       </script>
     </body>
     </html>
