It is an object of the present invention to minimize any sensation of inadequate firmness and large changes in deceleration rate with respect to a change in a brake operation force when the force exceeds a boost limit point. A first correlation S1 when a brake operation force increases and a second correlation S2 after hysteresis is applied at the time of a decrease in the brake operation force are taken as relationships between a brake operation force F and a wheel cylinder pressure PWC in a state wherein an assist hydraulic pressure PA is not applied. An assist hydraulic pressure control section controls the assist hydraulic pressure PA so that when a brake operation force that exceeds a boost limit point T1 is applied, the assist hydraulic pressure PA is added, hysteresis is applied when the brake operation force decreases, the assist hydraulic pressure PA decreases, and the relationship between the wheel cylinder pressure PWC and the brake operation force F when the assist hydraulic pressure PA decreases to zero becomes the second correlation S2.