To provide a throw-away type cutting tool preventing cracks of a tip due to excessive fastening stress and suppressing deviation of the tip in relation to stress from the horizontal direction.

In this throw away type cutting tool, a cutting edge tip 2 is held and fixed within a tip mounting part 3 provided at an end of a tool holder main body 1. A cross-sectional shape of a seated surface 9 of the cutting edge tip 2 is constituted of a substantial M-shape. A projection part 10 projected downward is formed at a tip width direction center position. A restricted tapered surface 11 ascending toward a side surface side of the tip 2 and a restricted tapered surface 13 descending toward the side surface side of the tip 2 are successively arranged on both adjacent sides. A cross-sectional shape of a facing holder side mounting surface 4 is constituted of a substantial M-shape engaged to the tip side seated surface 9. A recessed part 15 recessed downward is formed at the tip width direction center position. A restricted tapered surface 16, a flat surface 17 and a restricted tapered surface 18 are successively arranged on both adjacent sides.