To realize the excellent mountability of a brake rotor to a hub wheel to constitute a hub unit, and to enhance the workability of the hub wheel.

An enlarged part 28 is formed on a brake rotor mounting surface 25 side of a bolt hole 23 for mounting a brake rotor. The enlarged part 28 is formed of two tapered surfaces 28a, 28b having the different taper angles with respect to a center line of the bolt hole 23 inwardly from an opening edge 29 of the bolt hole 23. The taper angle of the tapered surface 28a on the opening edge 29 side is formed to be larger than the taper angle of the tapered surface 28b on its inner side. For machining a hub wheel 2 of this constitution, the brake rotor mounting surface 25 is finished after machining the bolt hole 23.