Traveling device for wheeled vehicle

A travel device (11) is provided with: a cylindrical mandrel (12); a rotating shaft (14) which is provided on the inner peripheral side of the mandrel (12) and which is rotated by the travel motor (13); a wheel mounting cylinder (16) which is rotatably provided on the outer peripheral side of the mandrel (12), to which a wheel (7) is mounted, and in which lubricating oil (L) is accommodated; a speed reduction mechanism (21) that decelerates the rotation of the rotating shaft (14) and transmits the rotation to the wheel mounting cylinder (16); a retainer (42) that has a bearing fitting hole (42A) and is provided on the inner peripheral side of the mandrel (12); and a bearing (44) that is attached to the holder (42) and supports the rotating shaft (14). An annular flange part (42D) abutting against the bearing (44) is arranged on the surface of the retainer (42) on the side of the driving motor (13), and an oil storage piece (47) is arranged on the surface of the retainer (42) on the side of the speed reduction