To provide a hub unit capable of restricting the generation of burrs in the axial direction and eliminating the fall of the burrs even in the case of using a hub bolt having high hardness.

The hub unit 1 comprises an outer ring 2, a hub wheel 3, an inner ring 4 and rolling body rows 5 and 5. A hub flange 33 of the hub wheel 3 has a through hole 33a for press-fitting a hub bolt 36, and on the other hand, a serrated portion 362 of the hub bolt 36 is press-fitted in the through hole 33a, and the head 360 of the hub bolt is made to abut on the peripheral edge 330b of the insertion hole for fitting. The hardness of a steel material of the hub flange 33 is adjusted to HRC18-HRC28, and the hardness of a steel material of the hub bolt 36 is restricted to Hv400-Hv500. Furthermore, an opening peripheral portion 331c of the through hole 33a as the projecting side of the hub bolt 36 is enlarged in diameter by an outside tapered portion, and the vehicle outside edge 362a of the serrated portion 362 is positioned, retreated toward the inside of the vehicle from the vehicle outside edge 332c of the outside tapered portion 331c.