A machine tool includes a spindle device; a shutter which is disposed between a tool magazine disposed over a machining chamber and the machining chamber, and is capable of opening and closing; a tool exchange device; and a tool breakage detecting device to detect whether a tool indexed to a tool detecting position of the tool magazine has breakage or not, and performs a return step of returning a first tool to the tool magazine with use of the tool exchange device; an attachment step of attaching a second tool to the spindle device; and a breakage detecting step of rotatively moving the first tool returned to the tool magazine to the tool detecting position and detecting breakage of the first tool with use of the tool breakage detecting device, after the shutter is closed. This constitution can prevent erroneous detection and improve the operational efficiency of the machine tool.