To provide a bearing device for a driving wheel which improves working efficiency in assembly/disassembly and secures reliability and operation stability by eliminating circumferential looseness in a coupled part.

In a bearing device for a driving wheel, a hub wheel 1 and an inner ring 5 are integrally and plastically coupled by rock-caulking. An outside joint member 14 is internally fitted in the hub wheel 1 through a serration so as to allow torque transmission. An axial clearance δ is formed between an inner end surface of a caulking part 6 and a shoulder part 19. A serration 21 formed so as to gradually enlarge a groove diameter thereof toward the inner side from the outer side in the OPD measurement is formed in the outer periphery of a shaft part 20. A male screw 20b is formed in an end of the serration 21. While the hub wheel 1 and outside joint member 14 are axially fastened to each other by threadably engaging a fixing nut 23 with the male screw 20b, the shaft part 20 is made short. The fixing nut 23 and male screw 20b are accommodated in the inner peripheral surface of the hub wheel 1.