To easily and surely drill a hole of the desired depth by providing a stopper to regulate the drilling depth by a drill blade body in the drill blade body.

After the position on a drill blade body of a stopper 2 is determined corresponding to the drilling depth, the drill blade body 1 is fitted and fixed to a hand drill D. In this condition, a lead blade 5 is abutted on the prescribed position of a work W to be drilled, and the hand drill D is driven. The lead blade 5 forms a small hole 14 in the work W to be drilled, and then, a hole 10 Is formed by the drill blade body 1. When the depth of the hole 10 reaches the prescribed value, the stopper 2 is abutted on an opening edge 10a of the hole 10 to regulate further entering of the drill blade body 1 and achieve the chamfering of the opening edge 10a by a chamfering blade 8.