To constantly induce the body of a self-propelled vehicle to the center of a furrow path in the case of using guiding wheels at the front and rear ends of the frame of the self-propelled vehicle running through a furrow path in a culture house for preventing the riding of the vehicle on to a ridge by bringing the guide wheels into contact with the surface of the furrow path with a proper gripping force, thereby turning the wheels in vertical direction following the unevenness of the path and, when the guide of the vehicle is unnecessary, to facilitate the turn-round and the transfer of the vehicle body by turning and retracting the guiding wheels above the vehicle body.

A pair of guiding wheels 4 having grounding faces inclined outward relative to the traveling direction are pivoted to the right and left sides of the front and rear ends of a frame 1 of a vehicle body at positions protruded outside of driving wheels 2 in such a manner as to be turnable above and below the frame 1 by the aid of supporting arms 5. Springs 8 for retracting the right and left guiding wheels 4 toward the frame 1 are connected between the center part of the right and left supporting arms and the frame of the vehicle body.