In a vehicular brake system, an input piston and a pressure piston are coaxially and axially movably supported in a cylinder, and a brake pedal is coupled to the input piston. Pressure chambers formed on the axially opposite sides of the input piston communicate with each other via a communication passage. A control oil pressure can be supplied to a first supply port of the communication passage, and a reaction-force oil pressure can be supplied to a second supply port of a reaction-force chamber of the input piston, while braking oil pressures can be delivered from delivery ports of the respective pressure chambers.