PURPOSE: To make it possible to form simultaneously a prepared hole and a finished hole and to enable a highly precise finished hole to be formed, by providing finishing cutting blades extending a direction opposite to the spiral direction, and marginal sections in lands which have been formed spirally along the axis of a drill.

CONSTITUTION: When the forward end of a drill 10 making into contact with a workpiece is displaced in the direction B along the axis 18, the front edge parts of base sections 14 start to cut the workpiece so that cutting blades 24a through 24c for forming prepared holes cut the workpiece. Then, finishing cutting blades 30a through 30c make contact with the inner peripheral surface of the prepared hole to start finishing work so that the cutting blades 30a through 30c which project in the outer peripheral direction of the drill 10 further than the cutting blades 24a through 24c by L, cut the inner peripheral wall of the prepared hole to form a hole part. Then, marginal sections 34a through 34c adjacent to the cutting blandes 30a through 30c slide along the inner peripheral wall of the hole part so that varnish finish is made on the inner peripheral wall. Since the varnish finish may be effectively made, thereby it is possible to form an extremely precise hole.