A cutting insert, comprising: a polygonal shaped upper surface; a lower surface; a side surface connected to each of the upper surface and the lower surface; and an upper cutting edge located at an intersecting part of the upper surface and the side surface, wherein the upper surface comprises a first corner, and a second corner and a third corner respectively adjacent to both sides of the first corner, wherein the upper surface sequentially comprises a rake surface located along the upper cutting edge and inclined toward the lower surface as going inward from the upper cutting edge at a rake angle (β), and a connection surface located more inward than the rake surface and inclined toward the lower surface as going inward at a connection angle (γ), wherein the upper cutting edge sequentially comprises a corner cutting edge, and minor cutting edges and major cutting edges each major cutting edge being inclined toward the lower surface as going away from the corner cutting edge, wherein the corner cutting edge, a respective one of the minor cutting edges and a respective one of the major cutting edges are disposed in a direction from the first corner to each of the second corner and the third corner respectively, wherein the rake surface comprises a minor rake surface located inwardly of the minor cutting edges and inclined toward the lower surface as going inward at a first rake angle (β1), a major rake surface located inwardly of the major cutting edges and inclined toward the lower surface as going inward at a second rake angle (β2), and a corner rake surface located inwardly of the corner cutting edge and inclined toward the lower surface as going inward at a third rake angle (β3), characterised in that an intersecting part of the rake surface and the connection surface comprises highest positions in portions of the intersecting part located inwardly of the minor cutting edges. a polygonal shaped upper surface; a lower surface; a side surface connected to each of the upper surface and the lower surface; and an upper cutting edge located at an intersecting part of the upper surface and the side surface, wherein the upper surface comprises a first corner, and a second corner and a third corner respectively adjacent to both sides of the first corner, wherein the upper surface sequentially comprises a rake surface located along the upper cutting edge and inclined toward the lower surface as going inward from the upper cutting edge at a rake angle (β), and a connection surface located more inward than the rake surface and inclined toward the lower surface as going inward at a connection angle (γ), a rake surface located along the upper cutting edge and inclined toward the lower surface as going inward from the upper cutting edge at a rake angle (β), and a connection surface located more inward than the rake surface and inclined toward the lower surface as going inward at a connection angle (γ), wherein the upper cutting edge sequentially comprises a corner cutting edge, and minor cutting edges and major cutting edges each major cutting edge being inclined toward the lower surface as going away from the corner cutting edge, a corner cutting edge, and minor cutting edges and major cutting edges each major cutting edge being inclined toward the lower surface as going away from the corner cutting edge, wherein the corner cutting edge, a respective one of the minor cutting edges and a respective one of the major cutting edges are disposed in a direction from the first corner to each of the second corner and the third corner respectively, wherein the rake surface comprises a minor rake surface located inwardly of the minor cutting edges and inclined toward the lower surface as going inward at a first rake angle (β1), a major rake surface located inwardly of the major cutting edges and inclined toward the lower surface as going inward at a second rake angle (β2), and a corner rake surface located inwardly of the corner cutting edge and inclined toward the lower surface as going inward at a third rake angle (β3), characterised in that an intersecting part of the rake surface and the connection surface comprises highest positions in portions of the intersecting part located inwardly of the minor cutting edges. a minor rake surface located inwardly of the minor cutting edges and inclined toward the lower surface as going inward at a first rake angle (β1), a major rake surface located inwardly of the major cutting edges and inclined toward the lower surface as going inward at a second rake angle (β2), and a corner rake surface located inwardly of the corner cutting edge and inclined toward the lower surface as going inward at a third rake angle (β3), characterised in that an intersecting part of the rake surface and the connection surface comprises highest positions in portions of the intersecting part located inwardly of the minor cutting edges.