PURPOSE: To simplify the configuration of a valve by installing each inlet valve whose inflow side and outflow side are directly coupled with an assist pressure supply source and a main valve, respectively, in such an arrangement that the inlet valves are closed in the non-operating positions and opened with the changeover operation.

CONSTITUTION: The inflow sides of inlet valves 29 and 30 are connected through connection pipes 40 to a liquid pressure pump 26 and a pressure regulating valve 23 while the outflow sides of the inlet valves 29 and 30 are directly coupled with main valves 27 and 28 where check valves 41 and 42 are connected, and the outlet valves 35 and 36 are directly coupled with a reserver 20 through a return line 37. In this configuration, rotational tendency signals for wheels sensed by induction type sensors S1-S4 furnished on the wheels are fed to a logic processing circuit 44, which senses a lock tendency to conduct a slip control, and the pump 26 is driven so that an assist pressure is generated in the supply line 40. At the same time, the main valves 27 and 28 are changed over, and brake circuits I and II are isolated by the check valves 41 and 42, and the brake pressure is controlled. Thus a simple configuration is accomplished.