Dimple 4 has a side wall curved face 8 and an edge neighboring
curved face 9. The side wall curved face 8 is situated between a
point P4 positioned downward from the dimple edge Ed by the depth of 20%
in an in-depth direction and a point P3 positioned downward from the dimple
edge Ed by the depth of 50% in an in-depth direction. The edge neighboring curved
face 9 is situated between the dimple edge Ed and a point P5 positioned
downward from the dimple edge Ed by the depth of 10% in an in-depth direction.
Proportion of the number NL of dimples 4 having the diameter of equal to
or greater than 3.90 mm occupied in total number N of the dimples is equal to or
greater than 75%. Proportion of the number ML of dimples having the ratio (Re/Rw)
between a radius of curvature of Re of the edge neighboring curved face 9 and
a radius of curvature Rw of the side wall curved face 8 of 0.5 or greater
and 1.5 or less of equal to or greater than 75%, having the diameter of equal to
or greater than 3.90 mm and having the radius of curvature Re of 2.0 mm or greater
and 5.0 mm or less, occupied in the number NL is equal to or greater than 50%.