PURPOSE: To eliminate any damage and noise of a hydraulic device and improve the operational feeling thereof by increasing the stroke volume of a hydraulic motor rapidly when the hydraulic motor is stopped.

CONSTITUTION: A bypass conduit 53 communicated with a tank is connected to the pilot hydraulic circuit 50 of a pilot valve 51 and an ON-OFF valve 54 interlocked with a running control valve 22 is provided in the bypass conduit 53. When a hydraulic motor 20 is stopped, the ON-OFF valve 54 is so opened as to bypass the pilot pressure oil to the oil tank for releasing the pressure force of a volume control member 45, so that the stroke volume of the hydraulic motor 20 is increased rapidly. In as much as abnormal brake pressure force can thus be prevented from occurring in the conduit of the hydraulic motor 20 when the hydraulic motor 20 is stopped, any damage and noise of the hydraulic device can be eliminated and the operation feeling thereof can be improved.