To provide a wheel bearing device that can be made light in weight and small in size, reduces the number of processing man-hours, and can be made at lower cost through the simplification of assembly work.

An L-shaped ring 17 is fit into the inner diameter of a small-diameter step section 4b of a hub wheel 4. The L-shaped ring 17 is made of medium- or high-carbon steel containing 0.40 to 0.80 wt.% of carbon and is provided with a cylindrical interlocking section 17a that is press-fit into the inner diameter of the small-diameter step section 4b, and a circular plate section 17b extending outward in the radial direction from the interlocking section 17a. A face spline 18 is formed on the end face of the circular plate 17b and a serration 19, on which a prescribed hardened layer 21 with a surface hardness set within the range 50 to 64 HRC by high-frequency tempering is formed, is formed on the interlocking section 17a of the L-shaped ring 17. The bore 20 of the small-diameter step section 4b is untempered and is fit together tightly during machining with the serration 19, and the hub wheel 4 and the L-shaped ring 17 are joined by press-cut fitting.