A cutting insert (1, 10, 11, 12) comprising: two opposite end surfaces including a first end surface and a second end surface, each of them having an outline with a substantially polygonal shape; a peripheral side surface that extends between the first end surface and the second end surface; and a plurality of cutting edge sections (2A, 2B, 3A, 3B) that are formed along an intersecting ridgeline portion between the peripheral side surface and each of the first end surface and the second end surface, each of the cutting edge sections comprising: a corner cutting edge disposed at a corner portion; a major cutting edge connected with one end of the corner cutting edge; and a minor cutting edge connected with the other end of the corner cutting edge, wherein at least two cutting edge sections and a seating surface are formed on each of the first end surface and the second end surface, each of the cutting edge sections has a rake face (2e, 3e) on an adjacent end surface, at least a part of each of the cutting edge sections at least protrudes in an insert thickness direction, characterized by a non-cutting intersecting ridgeline area (2C, 2D, 3C, 3D) extending between adjacent cutting edge sections on either one of the first end surface and the second end surface is located adjacent, via the peripheral side surface, to at least a part of a portion including the corner cutting edge and the major cutting edge of an associating cutting edge section on the other one of the first end surface and the second end surface, wherein the seating surface on each of the first end surface and the second end surface extends to between the cutting edge sections (2A, 2B, 3A, 3B) and forms non-cutting intersecting ridgeline portions (9a, 9b, 9c, 9d) with the peripheral side surface. two opposite end surfaces including a first end surface and a second end surface, each of them having an outline with a substantially polygonal shape; a peripheral side surface that extends between the first end surface and the second end surface; and a plurality of cutting edge sections (2A, 2B, 3A, 3B) that are formed along an intersecting ridgeline portion between the peripheral side surface and each of the first end surface and the second end surface, each of the cutting edge sections comprising: a corner cutting edge disposed at a corner portion; a major cutting edge connected with one end of the corner cutting edge; and a minor cutting edge connected with the other end of the corner cutting edge, wherein a corner cutting edge disposed at a corner portion; a major cutting edge connected with one end of the corner cutting edge; and a minor cutting edge connected with the other end of the corner cutting edge, wherein at least two cutting edge sections and a seating surface are formed on each of the first end surface and the second end surface, each of the cutting edge sections has a rake face (2e, 3e) on an adjacent end surface, at least a part of each of the cutting edge sections at least protrudes in an insert thickness direction, characterized by a non-cutting intersecting ridgeline area (2C, 2D, 3C, 3D) extending between adjacent cutting edge sections on either one of the first end surface and the second end surface is located adjacent, via the peripheral side surface, to at least a part of a portion including the corner cutting edge and the major cutting edge of an associating cutting edge section on the other one of the first end surface and the second end surface, wherein the seating surface on each of the first end surface and the second end surface extends to between the cutting edge sections (2A, 2B, 3A, 3B) and forms non-cutting intersecting ridgeline portions (9a, 9b, 9c, 9d) with the peripheral side surface.