PURPOSE: To prevent the generation of a hydraulic-pressure difference between the hydraulic circuits of the both brake apparatuses without increasing the capacity of the both circuits by connecting the both hydraulic circuits through the first and the second always closed valves which are opened by the respective pistons operated by the respective brake hydraulic pressures in two systems.

CONSTITUTION: When either of two master cylinders 34 and 36 operates, a piston 18 is operated by the brake hydraulic pressure of a brake hydraulic circuit 37, and the valve piece 14 of an always closed valve is lifted from a valve seat 11b. Since another piston 23 does not operate and the valve piece 15 of another always closed valve is on a valve seat 12b, the brake hydraulic circuits 37 and 38 do not communicate, and brake is applied onto only a left rear wheel. When the both master cylinders 34 and 36 are operated at a same time, the brake hydraulic pressure of the both hydraulic circuits 37 and 38 act onto the pistons 18 and 23, and each piston 18 lifts-up the above-described valve pieces 14 and 15 from the valve seats 11b and 12b against springs 20 and 25. Therefore, the both hydraulic circuits 37 and 38 communicate, and a hydraulic-pressure difference is not generated.