To maintain the lifetime, and while to realize the efficient cutting and the smooth cut surface by providing two tip blades and three or more side surface cutting blades, and providing a cut part, of which tip is gradually connected to the tip blade, in a blade of the side surface cutting blades, which does not achieve the tip blade.

Two tip blades 21 and three or more side surface cutting blades 22 are provided, and a blade of both the side surface cutting blades 22, which does not achieve the tip blade 21, is provided with a cut part 3 to be gradually connected to the tip blade 21 at the tip thereof. Furthermore, in the tip blade 21, blade angle is formed larger, as it comes close to the tip from the periphery thereof. Angle of torsion of the side surface cutting blades 22 are desirably set at 20-50 degree. For example, in a ball end mill at 16mm of diameter, at 45 degree of angle of torsion and made of silicon nitride, four side surface cutting blades are provided, and two tip blades are provided. Blade angle is enlarged, as the diameter of the lateral cross sectional surface of the tip 21 is reduced.