A cutting insert, comprising: an insert body comprising: an upper surface; a lower surface; and a side surface intersecting with the upper surface and the lower surface; a cutting edge comprising: a corner cutting edge located at an intersection of the upper surface and the side surface and located at a corner section of first and second sides (22, 23) which constitute the upper surface; and a first cutting edge located at the first side; a rake face located along the cutting edge on the upper surface; and a protruding section located on an inner side on the upper surface with respect to the rake face, the protruding section comprising: a first surface inclined upward as approaching from the cutting edge to inside; a second surface located on a higher location with respect to the first surface and on the inner side with respect to the first surface based on the corner cutting edge, and inclined upward as approaching from the cutting edge to inside; and a third surface located between the first surface and the second surface; characterized in that an intersection portion of the first surface and the third surface is inclined downward as moving away from the corner cutting edge; the second surface comprises: a first inclined plane in a region corresponding to the corner section; and a second inclined plane located on an inner side of the first inclined plane, wherein an inclination angle (θ721) with respect to the lower surface of the first inclined plane is larger than an inclination angle (θ722) with respect to the lower surface of the second inclined plane; and the third surface is located intermittently between the first surface and the second surface. an insert body comprising: an upper surface; a lower surface; and a side surface intersecting with the upper surface and the lower surface; an upper surface; a lower surface; and a side surface intersecting with the upper surface and the lower surface; a cutting edge comprising: a corner cutting edge located at an intersection of the upper surface and the side surface and located at a corner section of first and second sides (22, 23) which constitute the upper surface; and a first cutting edge located at the first side; a corner cutting edge located at an intersection of the upper surface and the side surface and located at a corner section of first and second sides (22, 23) which constitute the upper surface; and a first cutting edge located at the first side; a rake face located along the cutting edge on the upper surface; and a protruding section located on an inner side on the upper surface with respect to the rake face, the protruding section comprising: a first surface inclined upward as approaching from the cutting edge to inside; a second surface located on a higher location with respect to the first surface and on the inner side with respect to the first surface based on the corner cutting edge, and inclined upward as approaching from the cutting edge to inside; and a third surface located between the first surface and the second surface; a first surface inclined upward as approaching from the cutting edge to inside; a second surface located on a higher location with respect to the first surface and on the inner side with respect to the first surface based on the corner cutting edge, and inclined upward as approaching from the cutting edge to inside; and a third surface located between the first surface and the second surface; characterized in that an intersection portion of the first surface and the third surface is inclined downward as moving away from the corner cutting edge; the second surface comprises: a first inclined plane in a region corresponding to the corner section; and a second inclined plane located on an inner side of the first inclined plane, wherein an inclination angle (θ721) with respect to the lower surface of the first inclined plane is larger than an inclination angle (θ722) with respect to the lower surface of the second inclined plane; and a first inclined plane in a region corresponding to the corner section; and a second inclined plane located on an inner side of the first inclined plane, wherein an inclination angle (θ721) with respect to the lower surface of the first inclined plane is larger than an inclination angle (θ722) with respect to the lower surface of the second inclined plane; and the third surface is located intermittently between the first surface and the second surface.