To provide a vibration control mechanism of an operating arm, capa ble of restraining vibration and noise of the operating arm to prevent a hydrau lic cylinder of the operating arm from being damaged.

A first bracket part 31 on the operating arm 11 side or a second bracket part 32 on the working device 20 side is provided with at least one pair of elastic members 323, 324, thereby elastically clamping a part of the second bracket part or the first bracket part to damp the vibration. The mechanism is provided with position regulating members 314, 315, 331, 340 adapted to abut on the second bracket part or the first bracket part to regulate the movement at least in one direction of three different directions.