A dump truck has a flange on an inner peripheral wall of a spindle. The flange arranges a support bearing for supporting a shaft. The spindle is formed of a chassis-side member and a reduction gear unit-side member joined together by welding. The chassis-side member is fixed on a chassis of the dump truck, and the reduction gear unit-side member is located closer to a side of the reduction gear unit than the chassis-side member. The reduction gear unit-side member is located on a side of an outer periphery of the shaft portion, where a distance to a coupling between the motor and shaft and a distance to a first sun gear between the reduction gear unit and shaft are equal to each other. On an inner peripheral wall of the reduction gear unit-side member, the flange is cast together with the reduction gear unit-side member.