A throw-away tip for a radius cutter and a throw-away radius cutter that exhibit enhanced cutting performance in high efficiency machining. The throw-away tip (1) has, as cutting edges, at least a circular arc edge (4a) shaped in a generally quarter circular arc and also has an outer edge (4b) extending from one end of the circular arc edge (4a), and the cutting edges (4a, 4b) are located at the intersection between a rake face (2) and a flank face (3). The throw-away tip (1) is adapted such that the rake face protrudes in a rotating direction when the throw-away tip (1) is attached to a tool body (10). In a cross section perpendicular to the cutting edges, the rake face (2) is tilted such that the further away the rake face (2) is from the circular arc edge (4a) and the outer edge (4b), the more gentle is the tilt of the rake face (2). The circular arc edge (4a) is formed protruded in the rotating direction. The edge ridge line of the outer edge (4b) is generally parallel to the axis of the tool body (10).