Wheel cylinders supplied with oil pressure from a master cylinder are respectively provided in brake mechanism provided in wheels of a vehicle. The wheel cylinder has a brake piston provided to form a first fluid chamber to supply oil pressure from the master cylinder, and a brake piston driven by the oil pressure of the first fluid chamber. The wheel cylinder has a piston mechanism formed by laminating thin plate shaped piezoelectric elements, and the piston mechanism is controlled to be expanded or contracted by controlling the voltage applied to the piezoelectric elements to vary the volume of the first fluid chamber. Cut-off valves are provided in passages for supplying the oil pressure from the master cylinder to the wheel cylinders, a check valve for allowing only the work oil to flow from the master cylinder to the wheel cylinder in parallel with the cut-off valve to control to expand the piston in the state the oil pressure is generated from the master cylinder and the cut-off valve is closed to control to further strengthen the oil pressure in the first fluid chamber.