To re-edit data automatically in case of needing different machining from usual in a numerically controlled machining system.

In a numerically controlled machining system including a CAM system 10, a CNC 14 and a machine 16, CAM data 12 including an action data part 26 and an index part 28 is prepared in the CAM system 10. The action data part 26 includes machining action data, measuring action data and supplementary machining action data, and the index part 28 includes a machining index and a corrective machining index. The machining index includes following work determining information by action results. After machining a workpiece 18 according to machining action data, the workpiece 18 is measured according to measuring action data. In case of machining insifficiency, the CNC 14 is made to re-edit the machining index on the basis of the following work determining information by action results so as to execute necessary supplementary machining automatically at the appropriate time.