PURPOSE: To facilitate the layout of a breakage detecting means which corresponds to plural tools mounted in close proximity on each other, and shorten the time required for turret indexing.

CONSTITUTION: After a breakage detecting head 43 is positioned on the axis along the longitudinal direction of tools 17, the detecting head is brought near the tip parts of the tools. In this constitution, a break detecting unit 21a can be mounted to a turning spindle 13. Further, since the break detecting unit 21a can be installed horizontally, a gear head 19 can be positioned at a detecting position V simply by turning a turret 15 through 90 degrees. Thus, the indexing time is reduced by half. Furthermore, since the positions of the detecting head 43 and the tools 17 are not shifted in the direction perpendicular to the axis when the breakage detecting head 43 is moved, the layout of the detecting head which corresponds to each tool can be easily performed even when plural tools are closely mounted on the gear head.