diff --git a/lib/core.js b/lib/core.js
index 8bf79bf..81fdc63 100644
--- a/lib/core.js
+++ b/lib/core.js
@@ -257,6 +257,25 @@ core.start = async (commander) => {
       return;
     }
     
+    // ネットワークエラー (WebClient.js からの DNS/接続エラー) はリトライ対象
+    if (isNetworkError && isNetworkError(error)) {
+      errorCount++;
+      if (now - lastErrorTime > ERROR_THROTTLE_MS) {
+        if (errorCount > 1) {
+          console.error(`RTM network errors occurred (${errorCount} times since last report)`);
+        } else {
+          console.error("RTM network error caught:", error.message || "Unknown network error");
+        }
+        lastErrorTime = now;
+        errorCount = 0;
+      }
+      if (!isReconnecting) {
+        isReconnecting = true;
+        scheduleRtmRestart();
+      }
+      return;
+    }
+
     // その他の予期しないエラーは通常通り処理
     throw error;
   });