A wheel support device, comprising: a hub spindle of a hub wheel to which a vehicle wheel is fitted; and an outer ring of a constant velocity joint, which is connected to the hub spindle such that power is able to be transmitted between the outer ring and the hub spindle, wherein a through-hole that passes through the hub spindle in an axial direction of the hub spindle is formed in the hub spindle, an outer ring shaft portion that is passed through the through-hole is formed in the outer ring, an inner-end first connecting portion of which an inner diameter gradually increases toward an axial outer side is formed in an inner end portion of the inner periphery of the hub spindle, which defines the through-hole, in the vehicle lateral direction; and an inner-end second connecting portion that is arranged radially inward of the inner -end first connecting portion and of which an outer diameter gradually increases toward an axial outer side is formed in an inner end portion of the outer ring shaft portion in the vehicle lateral direction, so as to correspond to the inner-end first connecting portion, and the inner-end first connecting portion (44 A) has spline teeth and the inner -end second connecting portion has spline teeth, and the spline teeth of the inner-end first connecting portion and the spline teeth of the inner-end second connecting portion mesh with each other, characterized in that an outer-end first connecting portion (44 B) of which an inner diameter gradually increases toward an axial outer side is formed in an outer end portion of an inner periphery of the hub spindle, which defines the through-hole, in a vehicle lateral direction, an outer-end second connecting portion that is arranged radially inward of the outer-end first connecting portion and of which an outer diameter gradually increases toward the axial outer side is formed in an outer end portion of the outer ring shaft portion in the vehicle lateral direction, so as to correspond to the outer-end first connecting portion, and the outer-end first connecting portion has spline teeth and the outer-end second connecting portion has spline teeth, and the spline teeth of the outer-end first connecting portion and the spline teeth of the outer-end second connecting portion mesh with each other. a hub spindle of a hub wheel to which a vehicle wheel is fitted; and an outer ring of a constant velocity joint, which is connected to the hub spindle such that power is able to be transmitted between the outer ring and the hub spindle, wherein a through-hole that passes through the hub spindle in an axial direction of the hub spindle is formed in the hub spindle, an outer ring shaft portion that is passed through the through-hole is formed in the outer ring, an inner-end first connecting portion of which an inner diameter gradually increases toward an axial outer side is formed in an inner end portion of the inner periphery of the hub spindle, which defines the through-hole, in the vehicle lateral direction; and an inner-end second connecting portion that is arranged radially inward of the inner -end first connecting portion and of which an outer diameter gradually increases toward an axial outer side is formed in an inner end portion of the outer ring shaft portion in the vehicle lateral direction, so as to correspond to the inner-end first connecting portion, and the inner-end first connecting portion (44 A) has spline teeth and the inner -end second connecting portion has spline teeth, and the spline teeth of the inner-end first connecting portion and the spline teeth of the inner-end second connecting portion mesh with each other, characterized in that an outer-end first connecting portion (44 B) of which an inner diameter gradually increases toward an axial outer side is formed in an outer end portion of an inner periphery of the hub spindle, which defines the through-hole, in a vehicle lateral direction, an outer-end second connecting portion that is arranged radially inward of the outer-end first connecting portion and of which an outer diameter gradually increases toward the axial outer side is formed in an outer end portion of the outer ring shaft portion in the vehicle lateral direction, so as to correspond to the outer-end first connecting portion, and the outer-end first connecting portion has spline teeth and the outer-end second connecting portion has spline teeth, and the spline teeth of the outer-end first connecting portion and the spline teeth of the outer-end second connecting portion mesh with each other.