PURPOSE: To improve the traveling performance by reducing the car width in the ordinary traveling where side wheels are raised by supporting the side wheel installed on the side part of a car body in free elevation and lowering for the car body and allowing said side wheels to be accommodated inside in the width direction of the body at the rising position in comparison with the case of the lowering position.

CONSTITUTION: If a motorcycle is brought into near stop through deceleration during the state where side wheels Ws are accommodated into the chained-line position, and a driver pulls a hand lever 26 in the A-direction to the position shown on the figure, a slide shaft 17 is shifted in the C-direction against a spring 18 through a torque tube 25, arm 27, etc. Then, a ring bracket 20 is pressed through a connecting rod 23, and a swing arm 7 turns around the axis line L of a bearing boss 4, and the side wheels Ws axially supported at the top edge are lowered to the position shown by the full line. At this time, the side wheel Ws is supported so that the side wheel Ws is accommodated inside in the axial direction of the car body with the rising attitude in comparison with the case of the lowering attitude, by the action of the inclination angle of the bearing boss 4.