A cutting insert includes a top face, a bottom face and a plurality of side walls extending between the top face and the bottom face. A peripheral cutting edge is defined at the juncture of each side wall and the top face. Each cutting edge includes a linear cutting edge portion and a concave cutting edge portion that curves inwardly in a plane that is perpendicular to a plane containing a central axis of the cutting insert. A radiused corner portion connects two adjacent cutting edges. Each linear cutting edge portion extends from one radiused corner portion to the concave cutting edge portion and the concave cutting edge portion extends from the linear cutting edge portion to another radiused corner portion.

Provided is a drill insert to ensure sufficient chipping resistance with respect to a large cutting load, which is detachably attached to a distal portion of a drill body which is rotated around an axis, in which a polygon face of a polygonal plate-shaped insert body is a rake face, a side face disposed around the rake face is a flank face, a cutting blade is formed on a ridge portion in which the rake face and the flank face intersect each other, the cutting blade includes a honing face, the honing face includes a first convex curved face continuous with the rake face and a second convex curved face continuous with the flank face, and in a cross section orthogonal to the cutting blade, a curvature radius of the first convex curved face is larger than a curvature radius of the second convex curved face.