PURPOSE: To steer left and right rear wheels surely in synchronization, with the compact constitution, by driving a suspension arm supporting member directly or through s link mechanism, through a driving lever by the power of a hydraulic motor.

CONSTITUTION: A rear wheel steering device is equipped with a driving mechanism for steering left and right rear wheels in the toe-in direction and toe-out direction by slide-shifting the lateral links 13L and 13R arranged before and behind a rear wheel supporting member, and the driving mechanism is equipped with a driving lever 35 which is swung through a wheel gear part 36 by turning a worm 37 by a hydraulic motor 40. A suspension arm supporting member 34 is directly driven by the swing movement of the driving lever 35, and the lateral link 13R is shifted in the axial direction, and a suspension supporting member 33 is driven through a link mechanism 35 by the swing movement of the driving lever 35, and the lateral link 13L is shifted in the axial direction, and rear wheels are steered.