To improve the slow turning performance of a vehicle and the safety of a steering brake device by providing a hydraulic release brake means and a hydraulic operation brake means.

In this device, when a pressurized oil is not supplied to the left hydraulic release brake oil chamber 43L of a left steering brake device 20L, a left hydraulic release brake piston 41L presses a brake disc 23 and a brake plate 24 by a spring 42 for pressurizing the brake so that a hydraulic release brake turns ON. When the pressurized oil is supplied, the piston 41L is moved to a left side and a left hydraulic release brake means 40L turns OFF. When the pressurized oil is supplied to a left hydraulic operation brake oil chamber 46L under the OFF state, a left hydraulic operation brake piston 45L presses the brake disc 23 and the brake plate 24 so that the hydraulic operation brake turns ON. When the pressurized oil is released, a left hydraulic operation brake means 44L turns OFF. Thus, a delicate brake operation is possible and a slow turning performance and safety are improved.