In a brake-by-wire brake system which includes a motor actuated cylinder configured to produce a brake fluid pressure according to an operating stroke thereof and an electric motor for actuating the motor actuated cylinder, the control mode is normally based on a fluid pressure control, but is switched to a stroke control when the brake pedal is released for the purpose of quickly reducing the operating stroke of the motor actuated cylinder to an initial value. To avoid a sudden increase in the noises of the electric motor at the time of switching from the fluid pressure control to the stroke control, a limit circuit limits electric current supplied to the electric motor when the control mode is switched from the fluid pressure control to the stroke control.