Cutting insert

A cutting insert having a first end surface, a second end surface opposite to the first end surface, and a peripheral side surface connecting the first end surface and the second end surface, wherein

• a first edge line at which the first end surface intersects the peripheral side surface is a rectangle having a first side and a third side as long sides and a second side and a fourth side as short sides;
• a cutting edge is respectively formed only at the first side, the second side, and the third side of the first edge line;
• and no cutting edge is formed at the fourth side of the first edge line;
• a second edge line at which the second end surface intersects the peripheral side surface is a rectangle having an identical shape to the first edge line;
• a sixth side where a cutting edge is formed is opposite to the fourth side, and an eighth side where a cutting edge is not formed is opposite to the second side;
• the peripheral side surface comprises a fourth side surface facing the fourth side and the sixth side;
• and
• the fourth side surface extends from the first end surface to the second end surface and is inclined in a direction from the second side to the fourth side.