To perform a smooth operation of a slope which is arranged in such a way that it may be drawn out of an entrance or exit of a bus.

A sub-frame 5 is provided which is constructed to advance or retract under a rotation of rollers 6 in respect to opposing two guide rails 3 arranged below a floor surface 1 at an entrance or exit of a bus, and a slope 4 pivotally arranged at a front end of the sub-frame 5. Rectangular shaped-rails 10, 11 are installed at roller contacting portions of the guide rails 3, and the rollers 6 rotatably arranged in the sub-frame 5 are formed with grooves coincided with the rail shape.