Travel devices for a transport vehicle are arranged in a longitudinal direction and a width direction of a loading platform to allow traveling of the loading platform. In this travel device, an arm includes an upper end turnably supported at a lower portion of the loading platform. The arm includes a lower end where an axle box is supported swingably in up and down directions. A wheel has a mid-plane that intersects with a swing plane of an axle shaft disposed at the axle box, and is supported at the axle shaft. Accordingly, this ensures a small vehicle width L2 of the transport vehicle.