The NC device of the machining center has the data memory for storing exchange history and data concerning a tool therein when the tool has been manually exchanged. When the data concerning the tool is updated, the data memory also stores update history. The main control unit determines whether the tool is changed on the basis of at least either of the exchange history and the update history. On the basis of a determination result, the main control unit controls the spindle head moving unit to stop the tool as well as allows a caution about the tool to be displayed on the display unit.