PURPOSE: To make possible simultaneously control the antilock of front and rear wheels, by controlling the antilock of the front wheels by high select method and that of the rear wheels by low select method.

CONSTITUTION: A front right wheel brake 19 and a rear left brake 38, and a front left wheel brake 19' and a rear right wheel brake 38' have respective brake systems. A hydraulic pressure governor 5 performs the control of the front wheel brakes while a hydraulic pressure governor 24 performs the control of the rear wheel brakes. A pressure introduction control valve 41 and a pressure evacuation control valve 42 control the pressure in a control hydraulic pressure chamber 14 thereby a piston 11 is pushed back to reduce the pressure in secondary brake hydraulic pressure chamber 13. Since electromagnetic valves 41, 42 of the front wheels are controlled by high select method whereas electromagnetic valves 43, 44 are controlled by low select method, brake control can be done in conformity with the load, and the directional stability and the steerability would not be affected adversely.