The utility model discloses a thread milling cutter for a ball, which consists of a cutting taper (1), a rod part (2) and a taper shank (3), wherein a chip room is a straight flute, and an edge part of the cutting taper is in a tooth shape of a double-arc eccentric form relieved tooth. The utility model has the beneficial effects that the thread milling cutter for the ball is an integral milling cutter which is specially used for processing threads in the ball, scrap iron is discharged as fragments and can not scrape a processed and molded surface, the processed threads have good surface quality, stable shape size, high work efficiency and low cost, the same cutter can process left-handed threads and right-handed threads, and the size of a pitch circle of the threads can be randomly adjusted as required.