Two-tiered dimples 8 of a golf ball have a first recessed part X and a
second recessed part Y. The first recessed part X substantially forms a
part of a spherical shape. The first recessed part X includes a first
opening 14, a side wall curved face 16 and a flat face 18. The second
recessed part Y is substantially a regular quadrangular pyramid. This
second recessed part Y includes a second opening 20, a slope 22 and a
bottom face 24. The second opening 20 is a regular tetragon. The first
recessed part X improves aerodynamic symmetry of the golf ball. The
second recessed part Y improves a dimple effect. Proportion of the number
of the two-tiered dimples 8 to total number of the dimples is equal to or
greater than 70%.