To suppress the decline of a traveling speed by varying the inclination of a guide roller corresponding to the inclination of a traveling road surface.

In the case that a four-wheel drive fence car 50 travels on a road surface C1, a pair of the upper and lower wall surface rollers 2a of a wall surface roller member 2 connected and supported by a swing arm member 3 are rotated while being abutted to a fence C2, a road surface roller 7 pivotally supported by the swing arm 3b of the swing arm member 3 is rotated while being abutted to the road surface C1 and the travel of the four-wheel drive fence car 50 is guided. The swing arm 3b of the swing arm member 3 is energized toward the road surface C1 by a spring member 6 and the swing arm member is swung in a vertical direction corresponding to the inclination of the road surface C1 since it is swingably supported by supporting stays 5 through a swing shaft 4. In such a manner, by the swing of the swing arm member 3 corresponding to the inclination of the road surface C1, the inclination of the wall surface rollers 2a of a pair of the wall surface roller members 2 is varied.