A hub assembly includes an axle having one end mounted fittingly in a metal socket member. A hub body includes a cylindrical wall formed integrally with a base wall and extending uprightly from an inner surface of the base wall, and a coupling tube formed integrally on the inner surface of the base wall. The cylindrical wall has a central axis transverse to the base wall. The coupling tube extends along the central axis, and has the socket member fixed therein.