A cavity iron golf club head being forme from a metal ingot by a rotary cutting tool that has a conical cutting section and a cylindrical cutting section which are formed into an integral unit in tow stages with the respective cutting surface angles differing from each other. An inner circumferential surface on the head sole side of an indentation formed in the back surface of the metal ingot which has been roughly finished and formed in cut into an overhanging surface shape by the conical cutting section and cylindrical cutting section of the rotary cutting tool, and the other inner circumferential surfaces on the toe and heel sides and on the top side of the metal ingot are cut into upright surface shapes by the cylindrical cutting section of the rotary cutting tool.