PURPOSE: To embody the light weight of a clutch drum in a vehicle, effectively solve problems such as the defective swell of tooth form and partial thinning in an existing sheet metal clutch drum formed by deep drawing, and cope easily with the change of spline length.

CONSTITUTION: An extruded aluminum pipe body with splines on the inner peripheral surface is cut into the fixed length to form an aluminum drum body 1A with splines 2A. A piston storage pan 3 formed of a separate member is then fixed fittingly to one end opening part of this aluminum drum body 1A.