A lock piston 64 operates to automatically lock a parking brake piston 53 which achieves a parking brake applied state in response to hydraulic pressure in a parking brake application control hydraulic chamber 54 and operates to release a locked state in response to hydraulic pressure in a parking brake release control hydraulic chamber 69, and a manual change-over unit 108 holding the hydraulic pressure in the parking brake release control hydraulic chamber 69 to a hydraulic pressure on a lock release side, is provided among the wheel brake side hydraulic path 76, the parking brake application control hydraulic chamber 54 and the parking brake release control hydraulic-chamber 69 by bypassing a hydraulic pressure control unit 87 which changes over the application or release of hydraulic pressure to the parking brake application control hydraulic chamber 54 and the parking brake release control hydraulic chamber 69.