Provided herein is a drill having less possibility of cracks in an inner periphery of a drilled workpiece and deformation of a workpiece upon penetrating with a drill, as well as delamination.
A drill according to the present invention comprises two cutting blades which are formed symmetrical about an axis of rotation, wherein each of the cutting blades has a main cutting blade formed from a drill tip toward a peripheral side of the drill to become a shape with curves, a thinning cutting blade in a shape with curves formed in closer to the drill tip than the main cutting blade, and an U-shaped cutting blade in a shape with curves formed in closer to the periphery of the drill than the thinning cutting blade.