A cutting insert formed of a plate-like member with a substantially polygonal outer shape and comprising: a rake face formed on at least one of opposite surfaces of the plate-like member; a flank formed on a side surface extended between the opposite surfaces; and a cutting edge formed at an intersecting portion where the rake face and the flank cross each other, the cutting edge comprising corner cutting edges formed at respective corner portions of the opposite surface with the rake face formed thereon and side cutting edges formed along a pair of side edge portions extending on opposite sides of each of the corner cutting edges, wherein a chip breaker groove is formed in the opposite surface with the rake face formed thereon and inside the corner cutting edge, the chip breaker groove comprises a raised portion raised upward from an interior of the chip breaker groove, the raised portion comprises a top surface comprising a top portion of the raised portion, a front raised surface facing the corner cutting edge and extended from the chip breaker groove to the top surface, and side raised surfaces arranged on opposite sides of the front raised surface and the top surface crosses both the front raised surface and each of the side raised surfaces, the front raised surface and the top surface intersect with each other at a first intersecting portion, a second intersecting portion at which each of the side raised surfaces and the top surface intersect with each other is extended from a corresponding one of opposite sides of the first intersecting portion and comprises a portion for which a distance from the corresponding side cutting edge increases gradually with a distance from the corner cutting edge, the front raised surface is curved so as to protrude outward, and the side raised surfaces are each curved so as to protrude outward, characterised in that the first intersecting portion is linearly extended. a rake face formed on at least one of opposite surfaces of the plate-like member; a flank formed on a side surface extended between the opposite surfaces; and a cutting edge formed at an intersecting portion where the rake face and the flank cross each other, the cutting edge comprising corner cutting edges formed at respective corner portions of the opposite surface with the rake face formed thereon and side cutting edges formed along a pair of side edge portions extending on opposite sides of each of the corner cutting edges, wherein a chip breaker groove is formed in the opposite surface with the rake face formed thereon and inside the corner cutting edge, the chip breaker groove comprises a raised portion raised upward from an interior of the chip breaker groove, the raised portion comprises a top surface comprising a top portion of the raised portion, a front raised surface facing the corner cutting edge and extended from the chip breaker groove to the top surface, and side raised surfaces arranged on opposite sides of the front raised surface and the top surface crosses both the front raised surface and each of the side raised surfaces, the front raised surface and the top surface intersect with each other at a first intersecting portion, a second intersecting portion at which each of the side raised surfaces and the top surface intersect with each other is extended from a corresponding one of opposite sides of the first intersecting portion and comprises a portion for which a distance from the corresponding side cutting edge increases gradually with a distance from the corner cutting edge, the front raised surface is curved so as to protrude outward, and the side raised surfaces are each curved so as to protrude outward, characterised in that the first intersecting portion is linearly extended.