A golf ball having a predetermined radius, and a spherical outer surface with a multiplicity of dimples formed therein. A protrusion is formed in each of the dimples which are located in hit portions having a diameter of 5 15 mm, or alternatively, is formed in each of all the dimples. The protrusion has a distal end whose radial distance from the center of the golf ball is equal to the predetermined radius of the golf ball. The protrusion has a partition wall which divides a space in each dimple into a plurality of segmental spaces. The protrusion may have two partition walls which are perpendicular to each other and intersect at right angles for dividing a space in each of the dimples into four segmental spaces.