An object of the present invention is to simplify a control during regenerative cooperation in a brake control system generating a hydraulic pressure in a master cylinder by displacing a piston with use of an electric actuator according an operation amount of a brake pedal. The brake control system displaces the primary piston 8 by controlling an operation of the electric motor 22 by a master pressure control unit 4 according to the operation amount Xop of the brake pedal 19, thereby generating a hydraulic pressure in the master cylinder 2 to supply it to wheel cylinders Ba to Bd. The master pressure control unit 4 sets a target relative displacement ΔXT between an input piston 17 and the primary piston 8 and a target hydraulic pressure PT in the master cylinder 2, and appropriately switch which is used to control a brake force. During regenerative cooperation, the master pressure control unit 4 selects the control with use of the target hydraulic pressure PT, which enables easy execution of a hydraulic pressure control including a subtraction of the hydraulic pressure corresponding to a brake effect from the regenerative cooperation.