PURPOSE: To enable the damping force of a shock absorber to be constantly controlled apparently with the position of piston stroke, regardless of displacement in the gradient angle of the force.

CONSTITUTION: There are provided a lower arm 17 with one end pivotally supported on a vehicle body 20 at a position nearly equal to the height of an axle section, and the other end fixed to the axle section, a shock absorber S with the end of a cylinder 2 pivotally supported on a part of the lower arm 17, and the end of a piston rod 3 pivotally supported on a part of the body 20 at a position higher than the axle section and slantingly laid, and a angle displacement sensor 31 at the side of the end of the cylinder 2 for detecting the angular displacement of the shock absorber S. A controller 32 is caused to output a throttle control signal for keeping constant the damping force of the shock absorber S against vertical body vibration velocity on the basis of angle displacement data from the sensor 31. Furthermore, a throttle control device 30 is caused to throttle and control a passage continuous to the first and second oil chambers 4 and 5 cellularized with a piston 1 in the cylinder 2, on the basis of a throttle control signal outputted from an external controller 32.