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