To enable the production of a golf ball having high repulsive performance with good productivity by irradiating the surface of the molded golf ball with IR rays and subjecting the surface to an annealing treatment at the time of production of the golf ball of which the outermost layer is composed of a composition composed of a crystalline polymer, such as an ionomer resin, as a chief material.

The crystalline polymer including the ionomer resin in a resin for the cover of the golf ball having a double layer structure has crystals partly in the molecule and consequently has the excellent characteristics, such as high repulsive performance and, therefore, this polymer is adequately used as the resin for the cover. Not these crystals exist in a sufficient amount right after the molding but the crystallization is accelerated by the annealing treatment (heat treatment) and the degree of crystallinity is improved. The surface of the molded golf ball is, thereupon, treated to be irradiated with IR rays at the time of the annealing treatment. At this time, the surface temperature of the golf ball is set at 40 to 70°C and the wavelength of the IR rays with which the surface is irradiated is set at a range of 2 to 20 μm.