PURPOSE: To facilitate parking of a vehicle in a spot having a short length in a longitudinal direction by a method wherein an auxiliary wheel driven by a drive means having an axis paralleling the longitudinal direction of a vehicle is retractably mounted in the vicinity of the central part of the lower rear part of a car body.

CONSTITUTION: A caseform body 15 is supported to a mounting member 10, fixed to a rear axle 51, around a shaft 16. An electric motor 18 is fixed in the body 15, and by gearing a worm gear 21 mounted on an output shaft 20 with a worm wheel 17 on the shaft 16, the body 15 is rotatable between a horizontal position and a vertical position. A moving member 30 which pivotally supports an auxiliary wheel 31 rotated through a worm gear 37 and a worm wheel 33 by running an electric motor 35 is engaged internally of the body 15. During rotation or the body 15 to the vertical side, the auxiliary wheel 31 is earthed. When the moving member 30 is raised against a spring 41 to turn ON a switch 41, control is made so that the electric motor 18 is stopped and the electric motor 35 is run.