A cutting insert comprising: a first surface; a second surface opposite to the first surface; a side surface continuous to both the first surface and the second surface; and a cutting edge constituted of a ridgeline between the first surface and the side surface, the first surface having a rake face continuous to the cutting edge, the cutting edge having a corner cutting edge, a flat cutting edge continuous to a first end portion of the corner cutting edge, and a main cutting edge continuous to a second end portion of the corner cutting edge opposite to the first end portion of the corner cutting edge, the rake face having a first rake face portion, a second rake face portion, and a third rake face portion, the first rake face portion being continuous to the flat cutting edge, the second rake face portion being continuous to the main cutting edge, the third rake face portion being continuous to the corner cutting edge and being located between the first rake face portion and the second rake face portion, the rake face being provided with a level difference portion at the second rake face portion or the third rake face portion, the level difference portion extending in a direction crossing the main cutting edge, the level difference portion being constituted of a rising surface, a first region, and a second region, the first region being adjacent to the rising surface at a side close to the corner cutting edge, the second region being adjacent to the rising surface at a side far from the corner cutting edge, the rising surface rising from the first region and being continuous to the second region, the main cutting edge including a first main cutting edge portion, a second main cutting edge portion, and a third main cutting edge portion continuous to the corner cutting edge, the first main cutting edge portion being continuous to the third main cutting edge portion at a first boundary portion, the first main cutting edge portion rising from the first boundary portion and being continuous to the second main cutting edge portion at a second boundary portion. a first surface; a second surface opposite to the first surface; a side surface continuous to both the first surface and the second surface; and a cutting edge constituted of a ridgeline between the first surface and the side surface, the first surface having a rake face continuous to the cutting edge, the cutting edge having a corner cutting edge, a flat cutting edge continuous to a first end portion of the corner cutting edge, and a main cutting edge continuous to a second end portion of the corner cutting edge opposite to the first end portion of the corner cutting edge, the rake face having a first rake face portion, a second rake face portion, and a third rake face portion, the first rake face portion being continuous to the flat cutting edge, the second rake face portion being continuous to the main cutting edge, the third rake face portion being continuous to the corner cutting edge and being located between the first rake face portion and the second rake face portion, the rake face being provided with a level difference portion at the second rake face portion or the third rake face portion, the level difference portion extending in a direction crossing the main cutting edge, the level difference portion being constituted of a rising surface, a first region, and a second region, the first region being adjacent to the rising surface at a side close to the corner cutting edge, the second region being adjacent to the rising surface at a side far from the corner cutting edge, the rising surface rising from the first region and being continuous to the second region, the main cutting edge including a first main cutting edge portion, a second main cutting edge portion, and a third main cutting edge portion continuous to the corner cutting edge, the first main cutting edge portion being continuous to the third main cutting edge portion at a first boundary portion, the first main cutting edge portion rising from the first boundary portion and being continuous to the second main cutting edge portion at a second boundary portion.