To prevent movement of a vehicle and deterioration of riding comfortableness caused by abrupt change of load by switching a circuit using an automatic height regulating valve to an auxiliary air feed/discharge circuit when the change is generated, and thereby controlling the height of air spring.

Under a running condition an upper air spring 7 is used for the adjustment of height, and pressurized air of which pressure is set to a specified level by a pressure reducing valve 3 so as to ensure the pressing force corresponding to the reaction force of a lower air spring 17 is supplied to the air spring 7. An auxiliary air feed/discharge circuit composed of switches 13, 15 detecting the height of the air spring and control valves 14, 16 is provided. When the switch 15 detecting that the height of the air spring 7 is made lower than a normal height is made ON, the valve 16 performs communicating of a pipe line connecting the spring 7 to an auxiliary air reservoir 19 to supply the spring with compressed air. When the switch 13 detecting that the spring 7 is made higher than the normal height is made ON, on the other hand, air is fed and discharged from the valve 14 to resume the spring 7 to the normal height.