To provide a tool breakage sensing device capable of accurately sensing eventual broken condition even if the tool has a small diameter without risk of any influencing the cycle time of working.

A tool breakage sensing device is provided in a machine tool 1 equipped with a tool magazine 10 to accommodate a tool T, a transporting means to transport the tool held by the magazine 10 to the changing position and accommodate the tool T having finished its work and returned from the mounted position on the spindle back to the changing position, and a tool changing means 15 to change the returned tool T with the one T transported to the changing position. The arrangement further includes photo-electric sensors 21 and 22 to cast the sensing light across the tool transport path and sense that the light is intercepted by the too; in movement and a breakage sensing means to sense whether the tool T is broken. Because tool breakage is sensed touchlessly, it is not required to interrupt the preparatory work for tool changing.