A bearing device for an axle: including a hub wheel; a flange outwardly provided in an outer periphery of the hub wheel in a radial direction; and bolts having serrations provided at their heads. The flange includes through holes formed therein in its circumferential direction such as to pass therethrough in its axial direction, the bolts are attached into the through holes, respectively, in a state where their serrations bite the through holes of the flange, and an annular groove for reducing a biting amount of the serrations of the bolt is formed in an inner peripheral surface of the through hole of the flange.