To maintain a fixed control clearance even if a pad is worn by fitting a flow control mechanism which limits hydraulic oil pushed out to a fixed amount, at the time of releasing braking, from a hydraulic cylinder which presses a spring and a pad that force a brake pad for clamping a disc rotor to the returning side.

During braking operation, a piston 11 is pushed to feed the hydraulic oil of an oil reservoir 10 to a hydraulic cylinder. When the piston 11 advances to a fixed limit, hydraulic oil passes through a check valve 13 by a lack amount from the back side of the piston 11 and fed to the hydraulic cylinder, and a brake pad clamps a disc rotor. At the time of releasing braking, the pad pushes out the hydraulic oil from the hydraulic cylinder by action of a spring, and the hydraulic oil is limited to the accommodation amount of the oil reservoir 10, so that the separating amount of the pad from the disc rotor is kept constant. The oil amount remaining in the hydraulic cylinder increases by the supply amount at the time of braking operation, therefore, the retreat position of the pad displaces to the disc rotor side according to its wear amount, thus keeping a braking clearance constant.