PURPOSE: To reduce the cost and to shorten the processing time by constructing such that a drill is held on a spindle section and rotated, while the side view shape of the drill is projected while being magnified through a magnifying projector then the image thereof is detected through an optical sensor and an indexing angle is calculated thereafter the drill is positioned at that position.

CONSTITUTION: A spindle section 11 holding a drill 16 is rotated and the rotary angle is detected through a rotary encoder 14. The side view shape of the drill 16 is projected onto the projection face 20 of a magnifying projector 17, then a V-shaped constricted portion 22 of a drill image 19 is detected through an optical sensor 22. An indexing angle is calculated based on a first rotary angle when one oblique side of the constricted portion 21 is detected and a second rotary angle when the other oblique side is detected. A controller 23 controls a servo motor 13 and positions the drill 16 with the indexed angle. Consequently, indexing can be made with an inexpensive optical sensor 22. Operation can be made easily with short time when compared with an image processor, resulting in shortening of indexing cycle time.