The cutting insert of the present disclosure, the a top surface having a first corner and a second corner adjacent to each other, a lower surface, and side surfaces, between the first corner and the second corner portion, and the upper surface comprising a cutting edge and a side surface located in the region that intersects, the. The cutting edge is first positioned between the first cutting edge located in the first corner portion side, the second cutting edge located at the second corner side, the first cutting edge and the second cutting edge 3 together have a cutting edge, viewed from the side, a concave curved shape on the lower surface side as from each of the first corner and the second corner toward the center of the cutting edge. Both the curvature radius of curvature R1 and the second cutting edge of the first cutting edge in the side view radius R2, smaller than the radius of curvature R3 of the third cutting edge in a side view. A cutting tool equipped with the cutting insert, provides a method of making a cutting workpiece using the cutting tool.