A throwaway insert and a cutting tool enable a high speed cutting operation for a metallic material having great ductility such as aluminum and obtaining a vertical wall with a high quality machined surface while improving chip control. The throwaway insert comprises a major cutting edge including a tapered cutting edge connected to a cutting edge of a nose portion, and a curved cutting edge connected to an end of the tapered cutting edge at a connection point. The curved cutting edge is formed so as to extend along an imaginary cylindrical surface whose center axis coincides with the axis of rotation of a tool main body, and tapered cutting edge is formed so as to gradually curve from the imaginary cylindrical surface toward the inside of the imaginary cylindrical surface as the distance from the curved cutting edge increases, and the distance from the nose portion decreases. The throwaway insert is attached to the tool main body in which the surface of the distal end thereof is machined so that surface roughness thereof is less than 3.2 μm when indicated by the Ry roughness.