To provide a hub unit for a wheel, preventing a step part between the shaft outer peripheral surface of a shaft body and a terminal end fitting part from causing overheat deformation affecting fitting of an inner ring element due to heat treatment without any increase in cost.

This hub unit for a wheel includes: an outer ring having first and second inner peripheral raceway tracks; and a hub provided with a first outer peripheral raceway track formed integrally with the shaft body opposite to the first inner peripheral raceway track of the outer ring and a second outer peripheral raceway track formed on the inner ring element externally fitted and fixed to the terminal end side fitting part of the shaft body opposite to the second inner peripheral raceway track of the outer ring, wherein a hardened layer having a predetermined depth is formed on the first outer peripheral raceway track of the shaft body, and a hardened layer having a predetermined depth is formed on the terminal end side fitting part to separately dispose the two hardened layers.