fluid from the actuator 12 is directed into a flow divider 16 via pipe 15 the fluid from the flow divider 16 is partially supplied to a power steering unit 20 via pipe 19 and partially to a brake booster 17 via pipe 18 the power steering unit 20 and the brake booster 17 are of the open center type and the fluid supplied thereto will return to the reservoir 13 respectively via pipes 22 21 the booster 17 is actuated by a brake pedal 23 to throttle the fluid passage between the pipes 18 and 21 due to the throttling the pressure in the pipe 18 is increased and this increased pressure is transmitted to a master cylinder 24 as power assist pressure for the pedal depression this boosting operation is conventional thus in the master cylinder 24 a pressurized fluid proportional to the pedal force is generated and transmitted to the front wheel brake cylinders 26 27 via pipe 25 and to the rear wheel brake cylinders 30 31 via pipe 28 actuator 12 and pipe 29 under normal braking when the wheels do not skid the wheel cylinders 26 27 30 31 are actuated to brake each wheel in accordance with the supplied fluid pressure the increased pressure in the booster 17 is also transmitted to the actuator 12 via pipes 18 and 32 this pressure is utilized as an input signal pressure for the actuation of the actuator 12 numerals 33 34 designate wheel sensing means for sensing the rotational conditions of the respective wheels and in response to the signals generated by the sensing means 33 34 computer 35 generates and transmits signals to the actuator 12 upon receipt of a pressure decreasing signal the actuator 12 will be actuated to.