To sufficiently reduce cutting resistance even when the depth of cut is large by using a throwaway tip having a chip breaker in a cutting blade in the case of double-cutting to which large cutting resistance is applied, and to prevent the throwaway tip and an end mill body for mounting it from being broken in cutting.

A cutting blade 5 is formed on the ridge line of a cutting face 2 and a flank 4 of the tip, and the cutting blade 5 is provided with the chip breaker 8. The thickness h of the tip along the cutting blade 5 is substantially constant. The chip breaker 8 is extended from the cutting blade 5 toward a bearing surface 3 up to the midway of the flank 4, and has an inclination to the direction of the thickness of the tip. The chip breaker is set to a length 1/2 to 3/4 times as large as the tip thickness h of the chip breaker 8.