PURPOSE: To unify the micro-texture of a junction section with that of a metal piece without performing the welding work.

CONSTITUTION: A golf club head having an outer shell structure is divided into multiple parts, a crown section 4 having a large radius of curvature is machined by the superplasticity machining method, a face section 5 having a small radius of curvature is machined by the press machining method, and a junction section between the crown section 4 and the face section 5 is forged and fayed in the high-temperature state. A faying die 7 mounted with the fayed crown section 4 and the face section 5 is stored in a chamber 8, and Ar gas is filled by pressure through the gas guide port 8a of the chamber 8 and held for a preset period while the chamber 8 is kept at the high-temperature state.