Abstract: SM valves 50FL, 50FR are in an open position which opens a line when electric power is OFF and are switched to a closed position when energized by a brake controller 30. These SM valves 50FL, 50FR are formed integrally with the pressure regulation valves (here, the closed position refers to the position (pressure regulation position) where the lines are opened when pressure applied from W/C 2FL, 2FR side is over a predetermined value and the SM valves function as pressure regulation valves). Also, restrictions 50FLS, 50FRS are provided across a switching region where the opening and closing of the SM valve 50FL, 50FR is executed in the M/C 234 side to apply pressure between the restrictions 50FLS, 50FRS and the switching region. In this way, aeration which occurs when high pressure fluid is returned to the M/C side is prevented and thus, vapor locks can be prevented.