To avoid the enlargement of an equipment, and improve the working efficiency by casting a hub insert by integrally forming an insert boss to constitute at least a part of a boss to support a wheel shaft and a brake drum to surround this in a concentric circle shape, into a hub.

An insert boss 7 and a brake drum 8 are integrally formed by a connecting part 13 of an almost cross shape in a side view, and the other part is formed as a lightening hole 14. In this hub insert, the insert boss 7, the brake drum 8 and the connecting part 13 are integrally performed by casting or the like, and afterwards, machine work is performed on a spline groove 9 and an inner peripheral surface of the brake drum 8. Particularly, the machine work of the brake drum 8 is true circle work to enhance concentric accuracy with the insert boss 7 as a reference and polishing work to obtain specific surface roughtness, and the circle work is easy in work since these are integrally formed with the insert boss 7, and the polishing work 19 also easy since a work object is comparatively small.