A vehicle height adjusting device comprises a vehicle height sensor (10) for sensing the height of a vehicle, means (30) for controlling the vehicle height which produces a vehicle height adjusting signal in response to the signal from the vehicle height sensor, driving means (20) for adjusting the vehicle height in response to the vehicle height adjusting signal, constant voltage conversion means (40) for converting a power supply voltage into a constant voltage and supplying the constant voltage to the means for controlling the vehicle height, and power supply control means for on-off controlling the supply of the power supply voltage in accordance with the turn-on and turn-off of an ignition switch. The vehicle height adjusting device further comprises means for stopping the power supply by a power supply stopping signal from the vehicle height control means when a predetermined time elapses after the ignition switch is turned off, and low voltage detecting means for stopping the operation of the means for controlling the vehicle height when the power supply is stopped and the output voltage from the constant voltage conversion means becomes lower than a predetermined reference voltage. An integrating circuit can be used in place of the low voltage detecting means. The vehicle height adjusting device performs an assured self-cut-off operation.