To improve the service life of a cutting edge while reducing damage to the cutting edge in cutting a ring material while rotating it.

In this ring material cutting method, the ring material W to be cut is moved forward toward the cutting edge 21 while being rotated, and after the ring material W is slit with the cutting edge 21 leaving only the preset dimension out of the thickness of the ring material W, the rotation of the ring material W is stopped. Further, after the ring material W is moved forward and slit to cut through only a part of the ring material W, the forward movement of the ring material W is stopped. The ring material W is rotated again to cut the remaining uncut part U. Consequently, since cutting conditions do not notably change when cutting through and cutting the uncut part U, a large force is not applied to one tooth of the cutting edge 21, which results in preventing damage to the cutting edge 21.