Ridged portions 200 projecting from the face 10 are formed in the edges of the scoreline 20. The ridged portions 200 are uniformly formed so as to extend in the longitudinal direction of the scoreline 20. FIG. 3A is an enlarged sectional view of the ridged portion 200. In this embodiment, the ridged portion 200 has a triangular cross-section, an inner side wall 201 on the side of the center of the scoreline 20, and an outer side wall 202 on the side opposite to the center of the scoreline 20. Also in this embodiment, the inner side wall 201 and side wall 21 are continuous with each other on nearly the same plane.

In this embodiment, the ridged portions 200 are formed to increase the amount of backspin on a struck ball. That is, as described above, the back spin amount on a struck ball typically increases or decreases nearly in proportion to the angle theta, but the formation of the ridged portions 200 makes it possible to obtain a sufficient amount of backspin even when the angle theta is relatively narrow.

A top 203 of the ridged portion 200 may be rounded off, as shown in FIG. 9A, so that the ridged portion 200 has a roughly triangular cross-section. Also, the top 203 may be shaped into a flat surface, as shown in FIG. 9B, so that the ridged portion 200 has a trapezoidal cross-section.