The hydraulic suspension system comprises a suspension mechanism (100) for a traveling vehicle body, a suspension reference position variation mechanism (18) for varying a reference position of a suspension stroke of the suspension mechanism, and a stopped state detector (58) for detecting a state in which operation of the suspension mechanism (100) has stopped. The control management unit (60) controls the suspension reference position variation mechanism (18) so that when operation of the suspension mechanism (100) is detected by the stopped state detector (58) to be in a stopped state, the operation of the suspension mechanism (100) moves toward a target range, in preference to control based on a suspension stroke position obtained from a suspension stroke position sensor (37).