To supply fluid to a fluid pressure cylinder by making use of traveling vibration, concerning a car height adjusting device using the fluid pressure cylinder for changing the height by supplying or discharging of fluid.

A shock absorber is constituted of a fluid pressure cylinder 10 for changing the car height by supplying or discharging of fluid. A pressure chamber 28 communicated with the fluid pressure cylinder 10 and a reservoir tank 40 is provided. A first cut valve is provided between the fluid pressure cylinder 10 and the pressure chamber 28. A second cut valve is provided between the reservoir tank 40 and the pressure chamber 28. A displacement member 30 to be displaced in response to the change of internal pressure of the pressure chamber 28, and pump mechanisms 32, 34, 42, 44 for force-feeding fluid in the reservoir tank 40 to the fluid pressure cylinder 10 are provided.