PURPOSE: To apply proper braking force according to body weight by controlling a cut-in point of an electromagnetic reducing valve by a signal from a load meter for detecting the body weight.

CONSTITUTION: The weight of the body 8 is detected with a load meter 7 and according to variation in the weight the detection signal is sent to an electromagnetic reducing valve 4 through a controller 9 to control the cut-in point of the valve. Thus, the reducing valve 4 adapted to be actuated by a command from the load meter matching the variations in the weight reduces oil pressure from a master cylinder 1 to the rear shaft brake system 3. With such an arrangement, a proper braking force is applied in response to the variations of the body weight to secure the accurate braking.