A machine tool, comprising: a spindle device for attaching a tool thereto to machine a workpiece; a machining chamber to cover a machining zone to machine the workpiece with the tool; a tool magazine disposed over the machining chamber, wherein the tool magazine stores a plurality of tools and is a rotational disc type magazine; a shutter disposed between the tool magazine and the machining chamber, the shutter being capable of opening and closing; a tool exchange device for exchanging the tool attached to the spindle device for a tool stored in the tool magazine; and a controller for controlling operations of the spindle device and the tool exchange device, wherein the controller is configured to perform: a return step of returning a first tool attached to the spindle device and used in the preceding process to the tool magazine; an attachment step of receiving a second tool to be used in the succeeding process from the tool magazine and attaching the second tool to the spindle device; and the machine tool characterized by comprising a tool breakage detecting device for detecting whether a tool indexed to a tool detecting position of the tool magazine has breakage or not; wherein the controller is further for controlling the tool breakage detecting device; wherein the controller is further configured to perform: a breakage detecting step (S2, S3) 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; and to judge whether a portion of the workpiece to be machined with the first tool is the same portion as a portion to be machined with the second tool or not, and wherein, in a case where a portion of the workpiece to be machined with the first tool is the same portion as a portion to be machined with the second tool, the controller gives an instruction to perform machining the workpiece with the second tool attached to the spindle device after the controller confirms that the first tool has no breakage in the breakage detecting step. a spindle device for attaching a tool thereto to machine a workpiece; a machining chamber to cover a machining zone to machine the workpiece with the tool; a tool magazine disposed over the machining chamber, wherein the tool magazine stores a plurality of tools and is a rotational disc type magazine; a shutter disposed between the tool magazine and the machining chamber, the shutter being capable of opening and closing; a tool exchange device for exchanging the tool attached to the spindle device for a tool stored in the tool magazine; and a controller for controlling operations of the spindle device and the tool exchange device, wherein the controller is configured to perform: a return step of returning a first tool attached to the spindle device and used in the preceding process to the tool magazine; an attachment step of receiving a second tool to be used in the succeeding process from the tool magazine and attaching the second tool to the spindle device; and the machine tool characterized by comprising a return step of returning a first tool attached to the spindle device and used in the preceding process to the tool magazine; an attachment step of receiving a second tool to be used in the succeeding process from the tool magazine and attaching the second tool to the spindle device; and the machine tool characterized by comprising a tool breakage detecting device for detecting whether a tool indexed to a tool detecting position of the tool magazine has breakage or not; wherein the controller is further for controlling the tool breakage detecting device; wherein the controller is further configured to perform: a breakage detecting step (S2, S3) 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; and to judge whether a portion of the workpiece to be machined with the first tool is the same portion as a portion to be machined with the second tool or not, and wherein the controller is further for controlling the tool breakage detecting device; wherein the controller is further configured to perform: a breakage detecting step (S2, S3) 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; and to judge whether a portion of the workpiece to be machined with the first tool is the same portion as a portion to be machined with the second tool or not, and wherein, in a case where a portion of the workpiece to be machined with the first tool is the same portion as a portion to be machined with the second tool, the controller gives an instruction to perform machining the workpiece with the second tool attached to the spindle device after the controller confirms that the first tool has no breakage in the breakage detecting step.