The invention provides a golf ball having a core and a cover of one layer or a plurality of layers, the core being formed of a material molded under heat from a rubber composition containing: (A) a base rubber, (B) an organic peroxide, and (C) water and/or a metal monocarboxylate. The core has a hardness profile which satisfies specific relationships between the JIS-C hardness at the core center (Cc), the JIS-C hardness at a position 10 mm from the core center (C10) and the JIS-C hardness at the core surface (Cs).