A cutting insert comprising a main body, the main body including: a first face ; a second face continuous with the first face and extending in a direction intersecting the first face ; and a third face continuous with the first face and the second face , the first face having a fixing hole formed therein, the second face including a rake face, among outer-peripheral sides of the second face , a boundary portion with the first face being a main cutting edge , when viewed from a side where the first face is disposed, the main cutting edge including: a first straight portion located adjacent to a reference side , the reference side being a boundary between the first face and the third face ; characterized in that the main cutting edge includes a second straight portion arranged at a distance from the first straight portion ; and a curved portion connecting the first straight portion and the second straight portion , a first intersection angle (θ1) of the first straight portion with respect to the reference side being different from a second intersection angle (θ2) of the second straight portion with respect to the reference side ; and wherein, when viewed from the side where the first face is disposed, the curved portion includes: a first curved sub-portion convex in a direction away from the fixing hole ; and a second curved sub-portion convex toward the fixing hole . a first face ; a second face continuous with the first face and extending in a direction intersecting the first face ; and a third face continuous with the first face and the second face , the first face having a fixing hole formed therein, the second face including a rake face, among outer-peripheral sides of the second face , a boundary portion with the first face being a main cutting edge , when viewed from a side where the first face is disposed, the main cutting edge including: a first straight portion located adjacent to a reference side , the reference side being a boundary between the first face and the third face ; characterized in that the main cutting edge includes a second straight portion arranged at a distance from the first straight portion ; and a curved portion connecting the first straight portion and the second straight portion , a first straight portion located adjacent to a reference side , the reference side being a boundary between the first face and the third face ; characterized in that the main cutting edge includes a second straight portion arranged at a distance from the first straight portion ; and a curved portion connecting the first straight portion and the second straight portion , a first intersection angle (θ1) of the first straight portion with respect to the reference side being different from a second intersection angle (θ2) of the second straight portion with respect to the reference side ; and wherein, when viewed from the side where the first face is disposed, the curved portion includes: a first curved sub-portion convex in a direction away from the fixing hole ; and a second curved sub-portion convex toward the fixing hole . a first curved sub-portion convex in a direction away from the fixing hole ; and a second curved sub-portion convex toward the fixing hole . <EOS>