A golf ball 2 includes a core 4, amid layer 6, a reinforcing layer 8, and a cover 10. The core 4 includes a center 12 and an envelope layer 14. The envelope layer 14 is formed by a rubber composition being crosslinked. The rubber composition includes a base rubber (a), a co-crosslinking agent (b), a crosslinking initiator (c), and an acid and/or a salt (d). The co-crosslinking agent (b) is: (b1) an alpha,beta-unsaturated carboxylic acid having 3 to 8 carbon atoms; or (b2) a metal salt of an alpha,beta-unsaturated carboxylic acid having 3 to 8 carbon atoms.