Cutting insert and indexable cutting tool

An indexable cutting insert comprising:

• a plate-like member having a substantially polygonal outer shape, top and bottom surfaces, and a central axis passing through the top and bottom surfaces, the cutting insert being indexable about the central axis;
• a rake face formed on at least the top surface;
• a flank extending between the top and bottom surfaces and being formed on an outer peripheral surface of the cutting insert;
• and
• at least one cutting edge formed at an intersection portion between the rake face and the flank, wherein:
• the cutting edge comprises a cutting corner portion, a first main cutting edge formed on one side of the cutting corner portion, and a second main cutting edge formed on the other side of the cutting corner portion;
• the second main cutting edge comprises:
• a descending inclination portion gradually inclined in a direction away from the top surface toward the bottom surface, as the descending inclination portion extends from the cutting corner portion in a direction away from the first main cutting edge;
• and
• an ascending inclination portion connected to the descending inclination portion, the ascending inclination portion gradually inclined in a direction toward the top surface, as the ascending inclination portion extends from the descending inclination portion in a direction further away from the cutting corner portion and the first main cutting edge;
• and
• at least a connection region of the ascending inclination portion and the descending inclination portion forms a concave curved non-cutting recess portion.