To perform optimal deburring/chamfering for a hole outlet by changing a hole inlet chamfering cutter inclined in the direction opposite a hole inlet deburring/chamfering cutter to be in parallel with a tool center line along a neck with respect to a tool rotational center axis.

For deburring, after penetration by a tool (drill) 91, a deburring cutter 92 is brought close to the outlet end of a machining hole by parallel moving the center of workpiece 90 or the drill 91 relative thereto, burrs are cut off by providing a notch, and chamfering is executed. When a face angle is provided, the rotational direction of a twist drill is made opposite to that when boring is performed because of the relationship of a twist groove. The chamfering of a hole outlet is simultaneously performed by a chamfering cutter 93. The moving amount of the tool relative to the workpiece is represented by x=Ecosθ, y=Esinθ in an orthognal coordinate (x, y), the variable eccentric amount of the tool center being E, and a turning angle being θ.