Travel drive device for dump truck

There are provided an axle housing (12), a rotational shaft (17) provided to axially extend in a spindle (14) of the axle housing (12), a wheel mounting cylinder (18) which is mounted on an outer peripheral side of the spindle (14) through wheel support bearings (20, 21) and to which wheels (7) are mounted, and a planetary gear reduction mechanism (25, 33) for decelerating rotation of the rotational shaft (17), which is transmitted to the wheel mounting cylinder (18). A carrier (38) forming a part of the planetary gear reduction mechanism (25, 33) is mounted in a non-rotating state on an open end side of the spindle (14). A cylindrical coupling member (51) is provided between the spindle (14) and the carrier (38), and provided with an axial one side outer periphery splined-coupled to an open end inner peripheral side of the spindle (14) and an axial other side outer periphery spline-coupled to an inner peripheral side of the carrier (38).