To keep positive contact between a driving wheel and a running plane for smooth run while maintaining stable attitude of an autonomous running vehicle.

An auxiliary wheel 170 is mounted on a chassis 101 via a suspension arm 140 rotatable around a suspension rotating shaft 133. The suspension arm 140 receives rotating force in the direction of pushing the auxiliary wheel 170 against a running plane from suspension springs 143a, 143b. When a distance between the shaft of a fixed auxiliary wheel 180 and the rear part 102 of the chassis is longer than a preset distance with the rotation of the chassis 101, it is detected by a microswitch 187, so that an energizing plate 160 is rotated in the direction of compressing an energizing spring 165. The compressive force of the energizing spring 165 is applied to a suspension arm 140 to more strongly pushing the auxiliary wheel 170 against the running plane and rotate the chassis 101 to be reset to an original position.