PURPOSE: To improve the stability of a driven ball and elongate a flown distance by molding a rolled material with superplastic working to weld respective molded parts to each other.

CONSTITUTION: Molds 10, 20 having molding cavities corresponding to respective contours of a plurality of parts made by dividing a golf club head are made of heat resisting steel. Also, upper molds 11, 21 corresponding to the molds 10, 20 are prepared. The upper molds 11, 21 are provided with gas introducing ports 12, 22. Rolled plates 30, 31 of thickness 5mm composed of 15.60% of A, 3.70% of V, 0.11% of O, 0.04% of N, 0.06% of C, 0.25% of Fe, 0.01% of H, remainder of Ti and inevitable impurities are disposed between the mold 10 and upper mold 11 and between the mold 20 and upper mold 21 and these members are all disposed in a superplastic molding machine to be heated to 850-950°C. Ar gas is forced in from the gas introducing ports 12, 21. Further, the rolled plates 30, 31 after the completion of the superplastic deformation are taken out of the molds 10, 20 and parts 32, 33 sandwiched by the mold are cut off and removed to weld the rolled plate 30 to the rolled plate 31.