A vehicle height adjustment device comprising: a changer (21, 22) configured to change a relative position of a body of a vehicle to an axle of a wheel (2, 3) of the vehicle; a detector (281, 282) configured to detect the relative position; and a controller configured to control the changer to change the relative position based on a detection value detected by the detector so as to control a height of the body as a vehicle height, the controller being configured to control the changer to maintain the vehicle height when there is a possibility of a malfunction in the detector, wherein the changer comprises: a spring comprising one end supported at a side of the body and another end supported at a side of the wheel, an adjustor comprising an accommodation chamber to accommodate a fluid and configured to adjust a length of the spring in accordance with an amount of the fluid in the accommodation chamber, a storage chamber storing the fluid, a pump comprising a cylinder, the pump being configured to suction the fluid stored in the storage chamber into the cylinder when a relative distance between the body and the wheel increases, and to discharge the fluid from the cylinder when the relative distance between the body and the wheel decreases, and a passage switch unit (300, 302) configured to switch states among a state of guiding the fluid discharged from the pump into the accommodation chamber to increase the amount of the fluid in the accommodation chamber, a state of guiding the fluid in the accommodation chamber into the storage chamber to decrease the amount of the fluid in the accommodation chamber, and a state of maintaining the amount of the fluid in the accommodation chamber, characterized in that the controller is configured to control the changer to maintain the state of maintaining the amount of the fluid in the accommodation chamber when there is the possibility of the malfunction in the detector. a changer (21, 22) configured to change a relative position of a body of a vehicle to an axle of a wheel (2, 3) of the vehicle; a detector (281, 282) configured to detect the relative position; and a controller configured to control the changer to change the relative position based on a detection value detected by the detector so as to control a height of the body as a vehicle height, the controller being configured to control the changer to maintain the vehicle height when there is a possibility of a malfunction in the detector, wherein the changer comprises: a spring comprising one end supported at a side of the body and another end supported at a side of the wheel, an adjustor comprising an accommodation chamber to accommodate a fluid and configured to adjust a length of the spring in accordance with an amount of the fluid in the accommodation chamber, a storage chamber storing the fluid, a pump comprising a cylinder, the pump being configured to suction the fluid stored in the storage chamber into the cylinder when a relative distance between the body and the wheel increases, and to discharge the fluid from the cylinder when the relative distance between the body and the wheel decreases, and a passage switch unit (300, 302) configured to switch states among a state of guiding the fluid discharged from the pump into the accommodation chamber to increase the amount of the fluid in the accommodation chamber, a state of guiding the fluid in the accommodation chamber into the storage chamber to decrease the amount of the fluid in the accommodation chamber, and a state of maintaining the amount of the fluid in the accommodation chamber, characterized in that the controller is configured to control the changer to maintain the state of maintaining the amount of the fluid in the accommodation chamber when there is the possibility of the malfunction in the detector. a spring comprising one end supported at a side of the body and another end supported at a side of the wheel, an adjustor comprising an accommodation chamber to accommodate a fluid and configured to adjust a length of the spring in accordance with an amount of the fluid in the accommodation chamber, a storage chamber storing the fluid, a pump comprising a cylinder, the pump being configured to suction the fluid stored in the storage chamber into the cylinder when a relative distance between the body and the wheel increases, and to discharge the fluid from the cylinder when the relative distance between the body and the wheel decreases, and a passage switch unit (300, 302) configured to switch states among a state of guiding the fluid discharged from the pump into the accommodation chamber to increase the amount of the fluid in the accommodation chamber, a state of guiding the fluid in the accommodation chamber into the storage chamber to decrease the amount of the fluid in the accommodation chamber, and a state of maintaining the amount of the fluid in the accommodation chamber, characterized in that the controller is configured to control the changer to maintain the state of maintaining the amount of the fluid in the accommodation chamber when there is the possibility of the malfunction in the detector.