Abstract: In a brake apparatus of the present invention, as MCY pressure is developed by a master cylinder (MCY) 1 according to the forward movement of a primary inner piston 9, a pump of a braking force control device arranged between the MCY 1 and wheel cylinders (WCYs) sucks up hydraulic fluid from the MCY 1 to discharge the hydraulic fluid to the WCYs. Thus, WCY pressure controlled according to operational conditions of various modes is developed. The WCY pressure is supplied to a control pressure chamber 40 to act on a step 8e of a primary outer piston 8. The primary outer piston 8 moves relative to the primary inner piston 9 in such a manner that the force produced by the MCY pressure, the force produced by the WCY pressure, the spring force of a control spring 13, and the frictional force of fluid-tightly slidable portions of the primary outer piston 8 are balanced, whereby the pedal travel can remain the same as that in service braking mode.