Cutting insert and cutting tool having the same

A cutting insert, comprising:

• an upper surface;
• a lower surface having a flat surface;
• a fastening hole penetrating the upper surface and the lower surface;
• side surfaces each connecting to the upper surface and the lower surface;
• and cutting edges formed by the upper surface and the side surfaces,
• wherein a first cutting edge among the cutting edges is inclined downward from one side to the other side,
• a major side surface among the side surfaces comprises a first major side surface connected to the upper surface so as to constitute the first cutting edge, and a second major side surface connected to the first major side surface and the lower surface, wherein the first major side surface has a negative surface, and the second major side surface has a positive surface, and
• a minor side surface among the side surfaces comprises a first minor side surface connected to the upper surface so as to constitute a second cutting edge, and a third minor side surface connected to the upper surface and the lower surface, wherein the first minor side surface has a positive surface, and the third minor side surface has a negative surface,
• wherein the one side is a high portion, and the other side is a low portion, and the upper surface is inclined from the high portion toward the fastening hole, and
• wherein the upper surface is composed of non-flat surface only.