Provided is a cutting insert (1) exhibiting excellent chip dischargeability under a wide range of cutting conditions, and also being capable of reducing cutting resistance and increasing wear resistance. The cutting insert is provided with: a cutting blade (6) having a polygonal top surface (2), bottom surface, (3) and side surface (4), the cutting blade being positioned at the intersection portion of the top surface (2) and the side surface (4), and being provided including a corner section (5) of the top surface; a through hole (7) passing from the center portion of the top surface to the center portion of the bottom surface; a projecting portion (9) extending from the corner section (5) to the through hole (7) side; and a rake surface (8) extending from the corner section (5) between the cutting blade (6) and the projecting portion (9) to the through hole (7) side. In the top surface view, a terminal end (13a) on the through-hole (7) side of a boundary line (13) between the rake surface (8) and the projecting portion (9) is positioned closer to the through-hole (7) side than a perpendicular line (A) which: passes through the center point (M) of the line segment composed by the top edge section (11) of the through hole positioned on a bisector (B) that bisects the angle formed by the corner section (5), and the tip (5a) of the corner section (5); and is perpendicular to the bisector (B).