Travel drive device for dump truck

A wheel mounting cylinder (18) is rotatably provided on an outer peripheral side of an axle housing (12) through wheel support bearings (20, 21). A wet brake (45) is provided between the axle housing (12) and the wheel mounting cylinder (18) for applying a braking force to rotation of the wheel mounting cylinder (18). A seal mechanism (55) is provided between the wet brake (45) and the wheel support bearing (20) for keeping a cooling liquid (50) of the wet brake (45) in a sealed state to lubricant oil (100) in the wheel mounting cylinder (18). A foreign-object trapping portion (58, 62) is provided between the wheel support bearing (20) and the seal mechanism (55) for trapping foreign objects flowing from the seal mechanism (55) toward the wheel support bearing (20).