To provide a bearing device for a wheel, improved in reliability by increasing and stabilizing the fixing force of a hub-bolt.

In this bearing device for a wheel, one end part of a hub wheel 4 is integrally provided with a wheel fitting flange 6, a cutout is formed from the pitch circle diameter to the inside diameter side of a bolt insert hole 6a between bolt insert holes 6a away from the peripheries of the bolt insert holes 6a bored at equal spaces in the circumference of the wheel fitting flange 6, and hub bolts 7 having a serration 7a formed at the neck are pressed in the bolt insert holes 6a. The surface hardness of the hub bolt 7 is set to at least 35HRC, and the difference in hardness between the hub bolt 7 and the inner peripheral surface of the bolt insert hole 6a is set to 12HRC or more.