A cutting insert, comprising: an upper surface; a lower surface; a side surface; and a cutting edge which is located in an intersection region of the upper surface and the side surface, and comprises a major cutting edge, a flat cutting edge, and a minor cutting edge located between the major cutting edge and the flat cutting edge, wherein the cutting edge comprises sequentially, in a side view, an ascending portion inclined upward from the flat cutting edge to the major cutting edge with respect to a reference plane perpendicular to a central axis of the cutting insert, a top portion connected to the ascending portion, and a descending portion connected to the top portion and inclined downward with respect to the reference plane, wherein the upper surface comprises a rake surface located inward the cutting edge, the side surface comprises a first side surface, a second side surface, and a third side surface which are located sequentially in a direction along the cutting edge, the flat cutting edge is located in an intersection region of the third side surface and the upper surface, the minor cutting edge is located in an intersection region of the second side surface and the upper surface, is inclined with respect to the major cutting edge in a top view and is inclined at an inclination angle θ1 with respect to the flat cutting edge in a top view, the major cutting edge is located in an intersection region of the first side surface and the upper surface, and is inclined at an inclination angle θ2 with respect to the flat cutting edge in the top view, wherein, the rake surface comprises a first rake surface comprising a first major rake surface located inward the major cutting edge and a first minor rake surface located inward the minor cutting edge, which are inclined downward at a rake angle α with respect to the reference plane from a side of the cutting edge toward an inward portion, characterised in that, an inward side of the first minor rake surface is inclined at an inclination angle θ3 with respect to the minor cutting edge, and an inward side of the first major rake surface is inclined at an inclination angle θ4 with respect to the major cutting edge in the top view, and the inclination angles θ1 to θ4 satisfy relationships of θ1>θ2 and θ3<θ4. an upper surface; a lower surface; a side surface; and a cutting edge which is located in an intersection region of the upper surface and the side surface, and comprises a major cutting edge, a flat cutting edge, and a minor cutting edge located between the major cutting edge and the flat cutting edge, wherein the cutting edge comprises sequentially, in a side view, an ascending portion inclined upward from the flat cutting edge to the major cutting edge with respect to a reference plane perpendicular to a central axis of the cutting insert, a top portion connected to the ascending portion, and a descending portion connected to the top portion and inclined downward with respect to the reference plane, an ascending portion inclined upward from the flat cutting edge to the major cutting edge with respect to a reference plane perpendicular to a central axis of the cutting insert, a top portion connected to the ascending portion, and a descending portion connected to the top portion and inclined downward with respect to the reference plane, wherein the upper surface comprises a rake surface located inward the cutting edge, the side surface comprises a first side surface, a second side surface, and a third side surface which are located sequentially in a direction along the cutting edge, the flat cutting edge is located in an intersection region of the third side surface and the upper surface, the minor cutting edge is located in an intersection region of the second side surface and the upper surface, is inclined with respect to the major cutting edge in a top view and is inclined at an inclination angle θ1 with respect to the flat cutting edge in a top view, the major cutting edge is located in an intersection region of the first side surface and the upper surface, and is inclined at an inclination angle θ2 with respect to the flat cutting edge in the top view, wherein, the rake surface comprises a first rake surface comprising a first major rake surface located inward the major cutting edge and a first minor rake surface located inward the minor cutting edge, which are inclined downward at a rake angle α with respect to the reference plane from a side of the cutting edge toward an inward portion, characterised in that, an inward side of the first minor rake surface is inclined at an inclination angle θ3 with respect to the minor cutting edge, and an inward side of the first major rake surface is inclined at an inclination angle θ4 with respect to the major cutting edge in the top view, and the inclination angles θ1 to θ4 satisfy relationships of θ1>θ2 and θ3<θ4. a first rake surface comprising a first major rake surface located inward the major cutting edge and a first minor rake surface located inward the minor cutting edge, which are inclined downward at a rake angle α with respect to the reference plane from a side of the cutting edge toward an inward portion, characterised in that, an inward side of the first minor rake surface is inclined at an inclination angle θ3 with respect to the minor cutting edge, and an inward side of the first major rake surface is inclined at an inclination angle θ4 with respect to the major cutting edge in the top view, and the inclination angles θ1 to θ4 satisfy relationships of θ1>θ2 and θ3<θ4.