A door body includes a door main body, an upper guided portion provided to an upper portion of the door main body, and a lower guided portion provided to a lower portion of the door main body. A guide member includes an upper guide portion, a lower guide portion, and a restricting portion. The upper guide portion supports the upper guided portion from below while restricting movement of the upper guided portion along the fore and aft direction. The lower guide portion supports the lower guided portion from below while restricting movement of the lower guided portion along the fore and aft direction. The upper guided portion is moved upwardly away from the upper guide portion in the expanded support state. The restricting portion restricts movement of the door main body in the first direction in the expanded support state, and restricts movement of the door main body in the second direction in the expanded support state.