A traveling drive device for a dump truck is provided with an axle housing mounted to a vehicle body, a wheel mounting tube rotatably provided on the outer periphery side of the axle housing, a disk holding cylinder provided on the axial outside of the wheel mounting tube, a brake disk mounted to the disk holding cylinder, and a brake device for applying braking to the brake disk. The disk holding cylinder is configured by a cylindrical body to be mounted to the wheel mounting tube and a plurality of disk mounting legs provided on the cylindrical body. A plurality of U-shaped projections are provided on the outer periphery side of the brake disk at positions corresponding to the respective disk mounting legs. A recessed groove which fits on the disk mounting leg so as to hold a distal end thereof is provided in each of the U-shaped projections.
