A numerical control device includes: a control unit controlling movement of shafts of a machine tool by a position command according to a machining program and acquiring position information on the shafts; a monitoring point determination unit determining a monitoring point in the machining program and a monitoring shaft according to the type of an instruction or an instruction related to travel described in the machining program; and a monitoring unit monitoring whether error or deviation based on the position information at the monitoring point of the monitoring shaft exceeds a predetermined threshold, wherein the control unit controls movement of the shafts based on the monitoring result of the monitoring unit, and the numerical control device further comprises an analysis unit presenting whether the cause of the error or deviation is a mechanical factor or a control factor based on the monitoring result and outputting the analysis result.