Technology is provided that enables vehicle speed to be grasped more accurately utilized for adjusting vehicle height. A vehicle height adjusting device includes: a relative position changing device capable of changing relative positions of a vehicle body frame and a rear wheel of a vehicle; a vehicle speed grasping section configured to grasp vehicle speed, which is moving speed of the vehicle body frame; and a change-over valve control section configured to control the relative position changing device on the basis of the vehicle speed grasped by the vehicle speed grasping section and change the relative positions of the vehicle body frame and the rear wheel to adjust vehicle height, which is the height of the vehicle body frame. The vehicle speed grasping section grasps the vehicle speed on the basis of front wheel rotating speed, which is the rotating speed of a front wheel, and rear wheel rotating speed, which is the rotating speed of the rear wheel.