A machine tool comprising: a first spindle; a second spindle provided on a rear headstock to face the first spindle; a barstock supply unit for supplying an elongate rod to the first spindle; and a processing means including a tool for processing the barstock, characterized in that the machine tool further comprises: a workpiece clamp device provided on the rear headstock and adapted to grip a second material comprised of the barstock that has been removed from the first spindle as an old material; and a joining means for joining opposite end portions of the second material gripped by the workpiece clamp device and of a first material gripped by the first gripping means and comprised of a barstock newly supplied by the barstock supply unit, thereby to integrate the second material and the first material into a single barstock.