PURPOSE: To improve precision in measuring of the captioned device for adjusting height of an automatic two-wheeler by forming said device in such a manner as the upstream of a control valve is maintained close to the lowest limit of a target air pressure prior to opening the control valve provided between an air pump and an air chamber.

CONSTITUTION: An air pump 82 is driven by a command of a controller 96 and a pressure sensor 92 sends the pressure to the controller 96. When this pressure reaches the lowest limit of a target air pressure, the controller 96 opens a control valve 88 or 90 and pressurizes an air chamber 66 of an air spring 22. When the air chamber 66 reaches the target air pressure, a pump 82 is stopped and the control valve 88 or 90 is closed. At the time of decompressing the air chamber 66, the pump 82 is operated prior to opening the control valve 88 or 90 to raise the air pressure in the upstream side of the control valves 88, 90 to the lowest limit of the target air pressure. The above formation realizes improvement of precision in pressure measuring.