PURPOSE: To surely detect a broken edge by fixing a contact switch having a contact freely brought into contact with a tool at the tip of a rockable arm.

CONSTITUTION: When drill machining by a drill 15 and reamer machining by a reamer 16 are completed, a multi-axis machine tool 10 is separated from a work W, rotations of the drill 15 and the reamer 16 are stopped, and the work W is conveyed. The cylinder 26 of a broken edge detecting device 20 is operated during this time, a cylinder rod 26a is lifted, and an arm 22 is rocked in the lateral. direction of the drill 15 and the reamer 16 side. if a contact switch 23 is not turned on when the arm 22 is rocked toward the drill 15 and the reamer 16 side, a tool is immediately judged to have a broken edge, the multi-axis machine tool 10 is stopped, and an alarm 'broken edge' is displayed.