This invention provides a hollow golf club head including a metal plate portion provided with thin and thick portions. A medium thick portion having an intermediate thickness between the thicknesses of the thin and thick portions is formed at the boundary portion between the thin and thick portions. The thin and medium thick portions are formed by the steps of pressing the metal plate portion to form a recess in one surface of the metal plate portion and a projection on its other surface, performing chemical milling of the recess and a portion surrounding it, and removing the projection by grinding.