A ladder (10) in a multi-step structure includes: a first front connecting member (11) and a first rear connecting member (12) that are connected to a lateral side of a vehicle body (2) and between a wheel (5B) and an end (2B) of the vehicle body (2) and that are juxtaposed with a predetermined space in a vehicle front-back direction; a first step board (13) that is connected in a pivotally movable manner between respective lower ends of the first front connecting member (11) and the first rear connecting member (12); a second front connecting member (14) and a second rear connecting member (15), respective upper ends of which are connected in a pivotally movable manner to both ends of the first step board (13) in the vehicle front-back direction; and a second step board (16) that is connected in a pivotally movable manner between respective lower ends of the second front connecting member (14) and the second rear connecting member (15). In the first front connecting member (11) and the first rear connecting member (12), one near the wheel (5B) is fixed to the vehicle body (2) and the other near the end (2B) of the vehicle body (2) is connected in a pivotally movable manner to the vehicle body (2) and is foldable.