A wear amount of a working tool T during the machining of a workpiece is estimated during the machining, and a positional command generated in accordance with a predetermined machining program is sequentially corrected during the machining based on the estimated wear amount of the working tool T. The workpiece W is machined in accordance with the corrected positional command. Also, the wear amount of the working tool T upon the interruption of the machining operation is calculated, and the positional command generated in accordance with the predetermined machining program is corrected based on the calculated wear amount of the working tool so that a tool edge position of the working tool T upon the interruption of the machining operation coincides with the tool edge position of the working tool T upon the restart of the machining operation when the machining operation is restarted at a position where the machining operation has been interrupted. The workpiece is machined in accordance with the corrected positional command.