Wheel supporting device

A wheel supporting device includes: a hub unit (2) that has a rotary ring (11) having a first spline (25) on its axially inner end face (24); and a joint (3) that has an outer ring (32) having a second spline (38), meshing with the first spline (25), on its axially outer end face (37). At least one projection (51) included in a plurality of projections (50) of the first spline (25) projects in the axial direction by a larger amount than the remaining projections (50) of the first spline (25). When a crest (52) of the at least one projection (51) contacts a crest of one of projections (39) of the second spline (38), a play is caused between the rotary ring (11)and the outer ring (32) due to the at least one projection (51) that works as a fulcrum.