PURPOSE: To form a smooth cutting surface by positioning successive component cutting edges on a curved envelope defined by the rotation of a generator about the rotation axis of a cutting insert.

CONSTITUTION: A cutting edge in a cutting insert includes plural successive component cutting edges 17a-17c and intermediate cutting edges 19 located between the successive component cutting edges, wherein the trailing end of one component cutting edge is joined to the leading edge of the following component cutting edge through the intermediate edge 19 and the intermediate edge 19 is pointed from the trailing end of one component cutting edge toward the base edge 20. Further, the successive component cutting edges 17a-17c overlap during a cutting operation and are located on a curved envelope defined by the rotation of a generator about the rotational axis of the cutting insert. At this time, the generator is substantially coplanar with the rotational axis.