To use a JIS 1000 level aluminum plate having an excellent electric conductivity as a stock and moreover to prevent the peeling of plating.

This manufacturing method is composed of at least the aluminum plate pressed into a prescribed shape in order to make a cooling plate, a first process (1-1) forming zinc on the surface of a cylindrical aluminum electrode post with the zinc substituting treatment, a second process (1-2) plating Ni or Cu on the aluminum surface, a third process (1-3) soldering plural aluminum plates to the electrode post, and if necessary, a fourth process (1-4) plating Sn to the heat radiating fin after assembling is added.