Abstract: There is provided a Ti alloy hollow club head which is more lightweight yet capable of realizing a better repulsion force by adjusting weight and thickness of a club head plate, with its strength ensured. Ribs are formed by chemically polishing the inner surface of a material of a crown plate to a 0.3 to 0.9 mm thickness, and a 0.3 to 4 mm width, and then first concave portions are formed to a 0.2 to 0.5 mm thickness. Thus, strength of the crown plate can be ensured by the ribs, while making the thickness thereof as thin as possible.

Abstract: There is provided a Ti alloy hollow club head which is more lightweight yet capable of realizing a better repulsion force by adjusting weight and thickness of a club head plate, with its strength ensured. Ribs are formed by chemically polishing the inner surface of a material of a crown plate to a 0.3 to 0.9 mm thickness, and a 0.3 to 4 mm width, and then first concave portions are formed to a 0.2 to 0.5 mm thickness. Thus, strength of the crown plate can be ensured by the ribs, while making the thickness thereof as thin as possible.

Abstract: A golf club having an increased moment of inertia and improved ball-hitting directionality is provided. A metal hollow golf club head comprises: a face portion; a crown portion; and a sole portion, and when the golf club has a lie angle of 60° with its club head volume being within 470 cm3, a moment of inertia about the axial line centered on the plumb line passing through the golf club head center of gravity is 5000 to 6000 g-cm2. In order to increase the moment of inertia, the thickness of the center portion of the crown portion is reduced by chemical etching, and a mass, including the portion of mass reduction, is positioned in the sole portion on the side of the toe portion; moreover, the separation distance from the center of gravity to the mass is increased.