To provide a tool breakage detection device for a drill, a reamer, and an endmill, or the like capable of detecting breakage of body or tip end of the tool without occurrence of failure due to infiltration of coolant (liquid) or electrical overload.

The tool breakage detection device 1 detects existence of breakage by abutting a contact rod 18 projectingly provided in the orthogonal direction from a turning shaft 16 projected from a body case 2 to the tool, and outputs a signal in case of breakage, and is constituted so as not to have influence on durability or the like due to infiltration of coolant by performing the turning of the turning shaft 16 with a linear motion air-driven part 3. The device is constituted so that the breakage can be detected by a pressing amount of the tip end of the tool relative to the sensor contact surface by providing a plunger type contact sensor 35 detecting the breakage of the tool on an arm rod 33 projectingly provided in the orthogonal direction from the turning shaft 16 projected from the body case 2.