When a single door for opening and closing an opening in a body is opened outward with its lower part as a fulcrum, a plurality of plate-shaped steps of a foldable boarding ramp provided on an inner face of the door are swung in association with one another from a stored position along the inner face of the door to a deployed position to be used for ingress and egress of the passengers. Since the boarding ramp is folded into the stored position, it does not impair the space of a passenger compartment. Further, since the steps are folded into a position so as not to interfere with a window provided in an upper part of the door, they do not give an oppressed feeling to the passengers in the passenger compartment. The step is deployed to cover the window provided in the upper part of the door during use.