Abstract: The invention provides a rubber composition having high rebound resilience measured by a rebound resilience evaluation method which is excellent in measurement accuracy and can sufficiently evaluate the difference in performance between samples. The invention also provides a golf ball formed from the rubber composition. The invention further provides a golf ball having excellent flight performance owing to good hardness distribution measured by a hardness evaluation method which is excellent in measurement accuracy and can sufficiently evaluate the difference in performance between samples. The invention relates to a rubber composition having a specific radius of gyration Rg obtained by a predetermined curve fitting method. The invention also relates to a golf ball including a spherical core having at least one layer, and a cover having at least one layer disposed to cover the spherical core, wherein the golf ball satisfies a predetermined relation obtained by a predetermined curve fitting method.