CUTTING INSERT AND EXCHANGEABLE BLADE-TYPE ROTARY CUTTING TOOL

A cutting insert (1) of the present invention comprises a first end surface (2) and a second end surface (3) which are opposed to each other and a peripheral side surface (4) connecting the first end surface (2) and the second end surface (3), and has a central axis (O) defined so as to penetrate these end surfaces. A major cutting edge (8) and a minor cutting edge (10), which are connected via a corner cutting edge (9), are formed along an intersecting edge between the first end surface (2) and the peripheral side surface (4). The peripheral side surface has a first side surface part (4a) related to the major cutting edge and a second side surface part (4b) related to the minor cutting edge. The first side surface part (4a) gradually extends outward from the cutting insert, heading from the first end surface to the second end surface. When a second virtual plane (L1), which is substantially perpendicular to the central axis (O) and passes through the major cutting edge (8), is defined, an inclined part (3a), on a back side of the cutting edge, of the second end surface (3) is inclined so as to become more distant from the second virtual plane (L1), heading from the first side surface part (4a) to the central axis (O).