1. A NC data dividing and editing apparatus for a NC machine tool system including a plurality of NC machine tools having their operations controlled by NC data, comprising: a NC data dividing processor for dividing a series of machining data derived by processing a part program by a main processor into a plurality of machining element data each of which can be carried out by a single tool, and for storing said machining element data, each of said plurality of machining element data including start condition data, tool specifying data, operation data and end condition data; a job allocation processor for allocating jobs to said machine tools in response to information received from each machine tool conveying if the machine tool is continuing to operate, load conditions of tools on each machine tool, mounting conditions of tools on each machine tool and job precedence relations of said machining element data as a function of the machining time for each machine tool and the number of times of transfer of a workpiece between machine tools to accomplish said jobs to be allocated by said job allocation processor; and a NC data editing processor responsive to the job allocation by said job allocation processor for combining and editing selected ones of said plurality of machining element data divided by said NC data dividing processor for each of said machining tools and for reallocating one or more machining element data originally allocated to one or more machine tools by said job allocation processor to one or more additional machine tools on the basis of an updating of said information used for originally allocating information to said machine tools.