To improve durability of a hydraulic motor by applying a load to a hydraulic motor by a hydraulic circuit for a brake.

If an accelerator pedal 22a is stopped on, a control valve 11 is operated for having a hydraulic drive motor 12 driven with discharge oil from a hydraulic pump 10. When the accelerator pedal 22a is stepped on, a selector valve 32 releases the discharge oil of a hydraulic pump 31 wholly in a tank, and a load of a hydraulic brake pump 31 on the hydraulic motor 12 is small. If the stepping-on of the accelerator pedal 22a is ceased, the control valve 11 is switched in a neutral position and the hydraulic motor 12 is hydraulically braked. At the time, the selector valve 32 introduces the discharge oil of the hydraulic pump 31 into a relief valve 33 with the result that a pump discharge pressure becomes equal with a relief pressure, and then the load of the hydraulic brake pump 31 is used for brake force of the hydraulic motor 12.