To provide a compact vehicle height adjusting device for preventing damage of a sliding part by a vehicle height adjustment, by surely absorbing operation of a suspension by vibration and impact received from a road surface to a tire.

This vehicle height adjusting device includes: mount rubber 2 for absorbing the operation of the suspension 7 by vibration from the road surface; a sliding mechanism 30 constituted of an external cylinder 3 having a cylindrical part 14 and an annular part 15 fixed to a body 6, a center mount 4 having an annular connecting part 16 for connecting the mount rubber 2 and the body 6 and a cylindrical part 18 for guiding sliding of an internal piston seat 5, and the internal piston seat 5 having an annular part 21 for holding an upper end part of a spring 10 and sliding on an outer peripheral surface of the center mount 4 and a cylindrical part 22 sliding on an inner peripheral surface of the external cylinder 3; and an air supply port 9 for sliding the internal piston seat 5.