To provide a forming die for a golf ball, easy to discharge air and little generating a fin hard to remove.

This forming die includes a holding pin 7. The holding pin 7 includes a tip part 19 and a side wall 21. The side wall 21 includes six projecting parts 23 and six recessed parts 25. The projecting parts 23 are linear mountains and the recessed parts 25 are linear grooves. The projecting parts 23 and the recessed parts 25 are alternately disposed. The projecting parts 23 and the recessed parts 25 are extended in the axial direction of the holding pin 7. The projecting parts 23 and the recessed parts 25 are extended to the upper end of the side wall 21. The clearance between the projecting part 23 and a holding pin hole 15 is small, and the clearance between the recessed part 25 and the holding pin hole 15 is large. In forming a golf ball, the air is discharged by the recessed parts 25 and a fin is parted by the projecting parts 23.