Cutting insert and cutting tool on which same is mounted

A cutting insert comprising an upper surface and a lower surface facing opposite directions to each other, and first and second lateral surfaces connecting the upper surface and the lower surface and being adjacent to each other, wherein the cutting insert comprises:

• a first cutting edge part forming a boundary between the upper surface and the first lateral surface;
• a second cutting edge part forming a boundary between the upper surface and the second lateral surface;
• and
• a corner cutting edge connecting the first cutting edge part and the second cutting edge part,
• wherein the first cutting edge part comprises:
• a first main cutting edge forming one end at a portion spaced farthest away from the corner cutting edge;
• a first sub-cutting edge connected to the corner cutting edge;
• and
• a first auxiliary cutting edge connecting the first main cutting edge and the first sub-cutting edge so as to form a step therebetween,
• wherein the first sub-cutting edge and the corner cutting edge, when viewing the first lateral surface, form one straight line and are inclined upward in a direction opposite to a direction toward the lower surface while gradually going in the direction toward the second cutting edge part,
• wherein the second cutting edge part comprises a second main cutting edge forming one end at a portion contacting the corner cutting edge, and when the upper surface is an X-Y plane and a Z-axis passes through a center of the upper surface, viewing the first lateral surface after rotating the first lateral surface by 45 degrees with respect to the Z axis reveals that the first sub-cutting edge, the corner cutting edge, and the second main cutting edge form one straight line section and are inclined upward in a direction opposite to a direction toward the lower surface while gradually going in the direction toward the other end of the second main cutting edge, and
• wherein the first lateral surface comprises:
• an upper clearance surface contacting the first cutting edge part;
• a lower clearance surface contacting the lower surface;
• and
• an intermediate clearance surface connecting the upper clearance surface and the lower clearance surface.