Cutting insert and cutting tool

A cutting insert, comprising:

• two end surfaces having a plurality of corner parts and opposed to each other;
• a peripheral side surface extending between the two end surfaces;
• and
• a cutting edge formed at an intersecting edge between at least one of the two end surfaces and the peripheral side surface,
• the cutting edge having at least a first corner edge formed at a first corner part, a second corner edge formed at a second corner part adjacent to the first corner part, and a major cutting edge and an end cutting edge provided between the first and second corner edges and connected to each other,
• the end cutting edge having a circular-arc shape, which projects outward, as viewed from an end surface side, the end cutting edge having a width which is from 15% to 50% of a width of the cutting insert in a direction connecting an outer end of the first corner edge and an outer end of the second corner edge, the end cutting edge having an arc radius which is from ⅓ to 1/1 of the width of the cutting insert,
• the end cutting edge is provided across a center line passing through a center in a width-wise direction of the cutting insert and extending in a direction orthogonal to the widthwise direction as viewed from a side of a peripheral side surface, and a first end of the end cutting edge on a side of the major cutting edge is in a position higher than a second end of the end cutting edge on the opposite side to the major cutting edge,
• the end cutting edge includes a first curve, which projects upward, and a second curve, which projects downward, as viewed from the side of the peripheral side surface, the first curve is connected to the major cutting edge, and an angle formed between a straight line connecting opposed ends of the end cutting edge and a line orthogonal to the center line of the cutting insert is greater than 0° and smaller than 20°, and
• the end cutting edge has the first curve, the second curve, and a straight line provided between the first and second curves and continuously connected to the first and second curves.