Gear skiving was developed about 100 years ago for cutting internal gears at high productivity. However, significant problems have prevented skiving from being used widespread. But recent technologies made it to receive attentions. The present paper proposes an evaluation index for continual changing work of cutting edge for internal gear skiving. From the distribution of the proposed index, it was confirmed that work for cutting became large on trailing side of cutting edge at the end of cutting.Fu rthermore, the work for cutting at topland of cutter account for large part of all. Finally, the work for cutting with cutting edges change periodically and the tooth flank of internal gear after cutting could be undulation because of the vibration of the work for cutting.