To provide a wheel supporting system hardly generating a creep in a bearing.

A retainer ring 5 abutting on the end surface 8b of an inner ring 8b and having a pair of projections 18 projected from the inner peripheral surfaces of the retainer ring 5, and immersed into a pair of linear grooves 16 formed along an axial direction on the peripheral surface of an axle shaft 1 and moved to the outer side of a vehicle when the retainer ring 5 is fitted to the axle shaft 1, is rotated around the axis 1a of the axle shaft 1, and the pair of projections 18 are arranged in an annular groove 17 formed at the axle shaft 1. Thereby, the retainer ring 5 is made immovable in the axial direction, and not moved in the axial direction even if the creep is generated in the inner ring 8.