diff --git a/src/extension.ts b/src/extension.ts
index 26c9f99..605b829 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -28,7 +28,7 @@ export function activate(context: vscode.ExtensionContext) {
 		const panel = vscode.window.createWebviewPanel(
 			'imageEditor',
 			'ImageMarkPengent',
-			vscode.ViewColumn.One,
+			vscode.ViewColumn.Two,
 			{
 				enableScripts: true,
 				localResourceRoots: [vscode.Uri.file(path.dirname(uri.fsPath))]
diff --git a/src/webviewContent.ts b/src/webviewContent.ts
index d13d356..60be6cf 100644
--- a/src/webviewContent.ts
+++ b/src/webviewContent.ts
@@ -7,10 +7,39 @@ export function getWebviewContent(imageSrc: string): string {
       <title>ImageMarkPengent</title>
       <style>
         html, body { height: 100%; margin: 0; padding: 0; overflow: hidden; }
+        #toolbar {
+          position: absolute;
+          top: 10px;
+          left: 10px;
+          background: rgba(255,255,255,0.95);
+          border-radius: 6px;
+          box-shadow: 0 2px 8px #0002;
+          padding: 8px 12px;
+          z-index: 10;
+          display: flex;
+          gap: 8px;
+          align-items: center;
+          font-size: 14px;
+        }
         #canvas { display: block; width: 100vw; height: 100vh; background: #222; cursor: grab; }
+        .active-btn { background: #1976d2; color: #fff; border-radius: 4px; }
       </style>
     </head>
     <body>
+      <div id="toolbar">
+        <button id="moveBtn" class="active-btn">移動モード</button>
+        <button id="markBtn">マーク追加(Ctr+左クリック)</button>
+        <label>太さ:
+          <select id="lineWidth">
+            <option value="2">2px</option>
+            <option value="4">4px</option>
+            <option value="8">8px</option>
+          </select>
+        </label>
+        <label>色:
+          <input type="color" id="colorPicker" value="#ff0000" />
+        </label>
+      </div>
       <canvas id="canvas"></canvas>
       <script>
       const canvas = document.getElementById('canvas');
@@ -18,7 +47,14 @@ export function getWebviewContent(imageSrc: string): string {
       let img = new Image();
       img.src = "${imageSrc}";
 
-      // ズーム・パン用変数
+      // UI要素
+      const moveBtn = document.getElementById('moveBtn');
+      const markBtn = document.getElementById('markBtn');
+      const lineWidthSelect = document.getElementById('lineWidth');
+      const colorPicker = document.getElementById('colorPicker');
+
+      // 状態
+      let mode = 'move'; // 'move' or 'mark'
       let scale = 1;
       let minScale = 0.1;
       let maxScale = 10;
@@ -29,6 +65,60 @@ export function getWebviewContent(imageSrc: string): string {
       let dragStartY = 0;
       let lastOffsetX = 0;
       let lastOffsetY = 0;
+      let ctrlPressed = false;
+
+      // マーク（楕円）の配列
+      let marks = [];
+      // 一時的なマーク（ドラッグ中のプレビュー）
+      let tempMark = null;
+      let markStart = null;
+
+      // 設定
+      let markColor = colorPicker.value;
+      let markLineWidth = parseInt(lineWidthSelect.value, 10);
+
+      // UIイベント
+      moveBtn.onclick = () => setMode('move');
+      markBtn.onclick = () => setMode('mark');
+      lineWidthSelect.onchange = () => { markLineWidth = parseInt(lineWidthSelect.value, 10); draw(); };
+      colorPicker.oninput = () => { markColor = colorPicker.value; draw(); };
+
+      function setMode(newMode) {
+        mode = newMode;
+        if (mode === 'move') {
+          moveBtn.classList.add('active-btn');
+          markBtn.classList.remove('active-btn');
+          canvas.style.cursor = 'grab';
+        } else {
+          moveBtn.classList.remove('active-btn');
+          markBtn.classList.add('active-btn');
+          canvas.style.cursor = 'crosshair';
+        }
+        // プレビュー消去
+        tempMark = null;
+        markStart = null;
+        draw();
+      }
+
+      // Ctrlキー押下・離上で一時的にマーク追加モード
+      window.addEventListener('keydown', (e) => {
+        if (e.key === 'Control') {
+          ctrlPressed = true;
+          canvas.style.cursor = 'crosshair';
+        }
+        if (e.key === 'Escape') {
+          setMode('move');
+        }
+        if ((e.ctrlKey || e.metaKey) && e.key.toLowerCase() === 'z') {
+          undo();
+        }
+      });
+      window.addEventListener('keyup', (e) => {
+        if (e.key === 'Control') {
+          ctrlPressed = false;
+          if (mode === 'move') canvas.style.cursor = 'grab';
+        }
+      });
 
       // リサイズ対応
       function resizeCanvas() {
@@ -40,11 +130,9 @@ export function getWebviewContent(imageSrc: string): string {
 
       // 画像ロード後、初期ズーム・位置を計算
       img.onload = () => {
-        // 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();
@@ -56,6 +144,30 @@ export function getWebviewContent(imageSrc: string): string {
         ctx.save();
         ctx.setTransform(scale, 0, 0, scale, offsetX, offsetY);
         ctx.drawImage(img, 0, 0);
+        // マークをすべて描画
+        for (const mark of marks) {
+          drawEllipse(mark.x1, mark.y1, mark.x2, mark.y2, mark.color, mark.lineWidth);
+        }
+        // プレビュー中のマーク
+        if (tempMark) {
+          drawEllipse(tempMark.x1, tempMark.y1, tempMark.x2, tempMark.y2, tempMark.color, tempMark.lineWidth, true);
+        }
+        ctx.restore();
+      }
+
+      function drawEllipse(x1, y1, x2, y2, color, lineWidth, dashed = false) {
+        ctx.save();
+        ctx.beginPath();
+        const cx = (x1 + x2) / 2;
+        const cy = (y1 + y2) / 2;
+        const rx = Math.abs(x2 - x1) / 2;
+        const ry = Math.abs(y2 - y1) / 2;
+        ctx.ellipse(cx, cy, rx, ry, 0, 0, 2 * Math.PI);
+        ctx.strokeStyle = color;
+        ctx.lineWidth = lineWidth / scale;
+        if (dashed) ctx.setLineDash([6 / scale, 6 / scale]);
+        ctx.stroke();
+        ctx.setLineDash([]);
         ctx.restore();
       }
 
@@ -71,32 +183,71 @@ export function getWebviewContent(imageSrc: string): string {
           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
+      // --- マーク追加モード or Ctrl+ドラッグで楕円追加 ---
       canvas.addEventListener('mousedown', (e) => {
-        isDragging = true;
-        dragStartX = e.clientX;
-        dragStartY = e.clientY;
-        lastOffsetX = offsetX;
-        lastOffsetY = offsetY;
-        canvas.style.cursor = 'grabbing';
+        const rect = canvas.getBoundingClientRect();
+        const x = (e.clientX - rect.left - offsetX) / scale;
+        const y = (e.clientY - rect.top - offsetY) / scale;
+        if (mode === 'mark' || ctrlPressed) {
+          if (x >= 0 && y >= 0 && x <= img.width && y <= img.height) {
+            markStart = { x1: x, y1: y };
+            tempMark = { x1: x, y1: y, x2: x, y2: y, color: markColor, lineWidth: markLineWidth };
+          }
+        } else if (mode === 'move') {
+          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();
+        const rect = canvas.getBoundingClientRect();
+        const x = (e.clientX - rect.left - offsetX) / scale;
+        const y = (e.clientY - rect.top - offsetY) / scale;
+        if ((mode === 'mark' || ctrlPressed) && markStart) {
+          tempMark = { x1: markStart.x1, y1: markStart.y1, x2: x, y2: y, color: markColor, lineWidth: markLineWidth };
+          draw();
+        } else if (mode === 'move' && isDragging) {
+          offsetX = lastOffsetX + (e.clientX - dragStartX);
+          offsetY = lastOffsetY + (e.clientY - dragStartY);
+          draw();
+        }
       });
-      window.addEventListener('mouseup', () => {
-        isDragging = false;
-        canvas.style.cursor = 'grab';
+      window.addEventListener('mouseup', (e) => {
+        if ((mode === 'mark' || ctrlPressed) && markStart && tempMark) {
+          if (Math.abs(tempMark.x2 - tempMark.x1) >= 2 / scale && Math.abs(tempMark.y2 - tempMark.y1) >= 2 / scale) {
+            pushUndo();
+            marks.push({ ...tempMark });
+          }
+          markStart = null;
+          tempMark = null;
+          if (mode === 'mark') setMode('move');
+          draw();
+        } else if (mode === 'move' && isDragging) {
+          isDragging = false;
+          canvas.style.cursor = 'grab';
+        }
       });
 
+      let undoStack = [];
+      function pushUndo() {
+        undoStack.push(JSON.stringify(marks));
+        if (undoStack.length > 100) undoStack.shift();
+      }
+      function undo() {
+        if (undoStack.length > 0) {
+          marks = JSON.parse(undoStack.pop());
+          draw();
+        }
+      }
+
       // 初期リサイズ
       resizeCanvas();
       </script>
