A method of making a golf ball including a core and a cover, and having good workability and excellent productivity includes the steps of clamping a half mold having a semi-spherical cavity and a male plug mold having a semi-spherical convex, followed by injection molding fluoroplastic from an inlet vent through a runner to form a fluoroplastic thin film on the surface of the half mold, incorporating a pair of the two half molds having the fluoroplastic thin film, which is composed of an upper mold and a lower mold, into a core mold, placing a core composition in the cavity, press molding the core composition in the core mold through the fluoroplastic thin film to form a spherical core, and covering the core with a cover.