To provide a tool breakage detecting device capable of improving the working rate of a machine by detecting a breakage at the side and the tip of a tool without stopping the rotation of the tool by preventing its falling in a flute and a blade of a rotating tool and preventing the bending and bounding; and to provide a tool breakage detecting device preventing a malfunction when determining presence/absence of a tipping amount of a cutting blade slope face at the tip of the tool.

This tool breakage detecting device 1 is so constituted that a contact rod is defined as a belt-shaped hardened leaf having a sufficient width A laid across a helical flute 6a of a drill or the like (tool 6) for preventing the falling of the contact rod into the flute and the blade of the tool and, even if abutting on the flute and the blade of the rotating tool, it can escape by the characteristic of the spring. For detecting the breakage at the tip of the tool, the contact rod 5 is defined as a sheet metal pole whose cross section can be bent into L shape and which prevents the bending of the tool in the tip side axial direction.