The invention provides 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 has, as cutting edges, at least a circular arc edge shaped in a generally quarter circular arc and also has an outer edge extending from one end of the circular arc edge, and the cutting edges are located at the intersection between a rake face and a flank face. The throw-away tip is adapted such that the rake face protrudes in a rotating direction when the throw-away tip is attached to a tool body. In a cross section perpendicular to the cutting edges, the rake face is tilted such that the further away the rake face is from the circular arc edge and the outer edge, the more gentle is the tilt of the rake face. The circular arc edge is formed protruded in the rotating direction. The edge ridge line of the outer edge is generally parallel to the axis of the tool body. The circular arc edge is bent in a protruding form along the rotation direction of the circular arc edge towards the tool body, the outer edge and the circular arc edge are continuously connected, at the same time, to extend towards the opposite side of the rotation direction of the tool body along with from one connected end of the circular arc edge to another end.