To improve assembling workability of the axle of a vehicle such as automobile and improve quality of the axle.

Before a hub 2 is inserted through the outer circumferential part of an axle case 1, an oil seal 7 and a taper roller bearing 3 positioned on the front side in the inserting through direction of the hub and also the outer race 4A, the taper rollers 4B, and the inner race 4C of a taper roller bearing 4 positioned on the rear side in the inserting through direction of the hub are mounted on the inner circumferential face of the hub 2, the inner race 4C is locked with a bearing fixing jig 18 so as to be unable to move in the reverse direction of the inserting through direction, and after completing to insert the hub 2 through the outer circumferential part of the axle case 1, the jig 18 is remove. Hereby, when the hub 2 is inserted through the outer circumferential part of the axle case, centering between both the hub 2 and the axle case 1 is correctly performed, dislocation is hardly generated between the centers of both, and at this inserting through operation, there is no possibility to generate damage of the oil seal 7, the taper roller bearing 3, and the like.