A cutting insert has top and bottom surfaces in the thicknesswise direction, and front and rear surfaces in the widthwise direction. First and second cutting edges are formed in the lengthwise direction at intersection portions where the top surface intersects with the front and rear surfaces. Third and fourth cutting edges are formed in the lengthwise direction at intersection portions where the bottom surface intersects with the front and rear surfaces. The first to fourth cutting edges are divided by a plurality of recesses. The plurality of recesses are symmetric with respect to the lengthwise centerline (A), which runs between the first and third cutting edges on the front surface and are asymmetric with respect to the thicknesswise centerline (B) perpendicular to the lengthwise centerline (A).