When an unusual condition of a wheeled vehicle such as nose-diving caused by braking, squatting caused by an abrupt start or rolling caused by a turn is sensed, the damping force or the spring constant of each suspension unit, which serves as a shock absorbing unit, is temporarily increased to correct the position of the vehicle. The increased damping force or spring constant is maintained a predetermined period of time even after the unusual vehicle condition is settled, thereby preventing the vehicle body from tossing back due to the force of inertia.