To ensure the strength of a step part and to facilitate the protruding and recessing of a wheelchair slope plate housed in the lower surface of the step part.

The part of a frame member 17A corresponding to an entrance step part provided on a body is formed as a low-floor recess part 20, a rail frame to be arranged in the lateral direction of the low floor recess part 20 is abolished, this part is opened, and the bottom surface of the low-floor recess part 20 is reinforced with a reinforcing plate 21. Since the low-floor recess part 20 is cut out in the lateral direction, the step part continued to the floor surface of a cabin provided on the low-floor recess part 20 can be reduced by one step in the state of ensuring the strength. Further, since the rail frame is abolished, the step part can be extended to the entrance direction in a flat state, and the wheelchair slope plate housed in the difference-in-level part between the interior floor surface and the step part can be straight pulled out along the surface of the step part.