The present invention provides a method of manufacturing golf balls having a rubber core of at least one layer and a cover of at least one layer which encloses the rubber core, which method includes the step of molding at least one layer of the rubber core by directly injecting a rubber composition into a spherical cavity and vulcanizing the injected composition. This process enables the sphericity of the rubber core to be enhanced, the rubber materials to be used without waste, and balls of an excellent scuff resistance to be obtained.