A cutting insert comprising: at least one cutting edge formed on an intersecting ridge line portion between a rake surface and a flank, each cutting edge including a cutting edge portion extending along a corner portion and a pair of straight-line shaped cutting edge portions (10, 10a, 10b) respectively connecting to the cutting edge portion of the corner portion; and at least two ridges (12, 12a, 12b) formed to rise on the rake surface, wherein one of the at least two ridges extends from a portion of the rake surface inside the cutting edge portion of the corner portion toward a portion of the rake surface inside one of the pair of straight-line shaped cutting edge portions, wherein another one of the at least two ridges extends from a portion of the rake surface inside the cutting edge portion of the corner portion toward a portion of the rake surface inside the other one of the pair of straight-line shaped cutting edge portions, wherein the rake surface inclines so as to become closer to a center of the cutting insert in a thickness direction as a distance increases from the cutting edge, wherein a far end of each of the at least two ridges (12, 12a, 12b) is formed at a position closer to the center of the cutting insert in a thickness direction than a near end of the respective ridge (12, 12a, 12b) in a direction away from the cutting portion of the corner portion, wherein each of the at least two ridges (12, 12a, 12b) includes a portion in which an amount of rising of the respective ridge (12, 12a, 12b) from the rake surface is gradually increased as a distance from the cutting edge portion of the corner portion increases, wherein each one of the at least two ridges (12, 12a, 12b) extends in a curved shape to be convex toward a side of the cutting edge, characterised in that each of the at least two ridges (12, 12a, 12b) does not protrude more outside than the cutting edge in a thickness direction. at least one cutting edge formed on an intersecting ridge line portion between a rake surface and a flank, each cutting edge including a cutting edge portion extending along a corner portion and a pair of straight-line shaped cutting edge portions (10, 10a, 10b) respectively connecting to the cutting edge portion of the corner portion; and at least two ridges (12, 12a, 12b) formed to rise on the rake surface, wherein one of the at least two ridges extends from a portion of the rake surface inside the cutting edge portion of the corner portion toward a portion of the rake surface inside one of the pair of straight-line shaped cutting edge portions, wherein another one of the at least two ridges extends from a portion of the rake surface inside the cutting edge portion of the corner portion toward a portion of the rake surface inside the other one of the pair of straight-line shaped cutting edge portions, wherein the rake surface inclines so as to become closer to a center of the cutting insert in a thickness direction as a distance increases from the cutting edge, wherein a far end of each of the at least two ridges (12, 12a, 12b) is formed at a position closer to the center of the cutting insert in a thickness direction than a near end of the respective ridge (12, 12a, 12b) in a direction away from the cutting portion of the corner portion, wherein each of the at least two ridges (12, 12a, 12b) includes a portion in which an amount of rising of the respective ridge (12, 12a, 12b) from the rake surface is gradually increased as a distance from the cutting edge portion of the corner portion increases, wherein each one of the at least two ridges (12, 12a, 12b) extends in a curved shape to be convex toward a side of the cutting edge, characterised in that each of the at least two ridges (12, 12a, 12b) does not protrude more outside than the cutting edge in a thickness direction.