PURPOSE: To secure good riding quality in time of passing through a inflection point by setting a control gain to a small value when such a state that the absolute value of an acceleration variation signal is less than the threshold value is continued as long as the first reference time, but to a large value the other way when the second reference time elapsed since a point of time when it has exceeded the threshold value.

CONSTITUTION: A controller 6 integrates a vertical acceleration signal detected by an acceleration sensor 7, securing a vertical absolute speed, and this absolute value speed is multiplied by a control gain, thereby finding out a control desired value. In addition, the controller 6 outputs a control signal upon comparing this control desired value with storage data, setting a damping coefficient to a damping coefficient variable shock absorber 3. In succession, the controller 6 sets the control gain to a small value when such a state that the absolute value of an acceleration variable signal obtained after differentiating the acceleration signal is less than the threshold value is continued as long as the first reference time, but to a large value when the second reference time elapses since a point of time when it has exceeded the threshold value.