PURPOSE: To facilitate the generation of the machining program and to change the priority order of the machining program.

CONSTITUTION: When the same shaft is specified by machining programs of plural systems, a CPU 1 reads priority levels of machining out by previously registered systems and performs shaft control in order from the system having the top priority to cut a work. Other systems start cutting the work after systems having higher priority finish cutting the work. Consequently, the machining programs need not be generated while attention to the specification of the same shaft is paid. The priority levels can easily be changed by changing the registration order.