To provide a hydraulic cylinder with the function of a shock absorber by providing a selector valve for feeding pressure oil to one of two oil chambers of a hydraulic cylinder and discharging the pressure oil from the other chamber to a tank or communicating the respective oil chambers, and generating damping force at the communicating time at an intermediate part of an oil passage for connecting the switching valve to each oil chamber.

An axle load control device is provided with a selector valve 13a switched to feed pressure oil to one of two oil chambers V1, V2 of a hydraulic cylinder 1a from a pump 3 and to exhaust the pressure oil from the other oil chamber to a reservoir tank 5 or to communicate the respective oil chambers V1, V2 with each other, and damaging force generating mechanism S for generating damping force at the time of communicating the respective oil chambers is provided at an intermediate part of oil passages R1, R2 for connecting the selector valve 13a to the respective oil chambers V1, V2.