PURPOSE: To provide a fail-safe structure for an alignment control device which prevents the inner pressure of the drive system of an actuator for altering the caster angle of a wheel from rising abnormally when excessive road surface input is given.

CONSTITUTION: An alignment control device has actuators 7L, 7R which have a cylinder body 34 partitioned into the first and the second hydraulic chamber 38, 39 by a piston 37 and alter the caster angle of a wheel; a drive means for selectively supplying pressure oil from a hydraulic pump, 22 through solenoid valves 8L, 8R to the first and the second hydraulic chamber to actuate the actuator; and an ECU 10 for actuating the actuator so that an aimed caster angle may be obtained on the running state of a vehicle. Thus elastic rubber hoses 30A, 31A having fixed length are used for the first and the second oil passage 30, 31 to connect the first and the second hydraulic chamber with the solenoid valve, and excessive road surface input is absorbed by the expansion of the elastic rubber hose.