A head has a curvature radius R of a boundary portion between a hitting face and a crown surface, and has a curvature radius S of a boundary portion between the hitting face and a sole surface. The head has, on its toe side, a curvature radius Rt, a curvature radius St, a face height Ft, and a head thickness Tt. The head has, at its center, a curvature radius Rc, a curvature radius Sc, a face height Fc, and a head thickness Tc. The head 4 has, on its heel side, a curvature radius Rh, a curvature radius Sh, a face height Fh, and a head thickness Th. Ft/Tt is smaller than Fh/Th. The head satisfies the following relationship (a) and/or (b): Rt>Rc≥Rh; St>Sc≥Sh.