In step S11, quantities that are varied (parameters) are respectively varied in a stepwise manner at a specified pitch, and standard working conditions consisting of combinations of these parameters are determined. For all of the standard working conditions, a working is actually performed, and the treated shapes that are obtained as a result are taken as the standard treated shapes for the respective standard working conditions (step S12). In cases where an appropriate simulation program is available, the standard treated shapes may be determined by simulation without actually performing a working. The standard working conditions and standard treated shapes thus determined are stored in a memory device. When the desired shape that is to be obtained by working is given in step S13, a standard treated shape that is close to the desired shape is sought in step S14. Thus, when a treated shape is given, the working conditions for this treated shape can be determined.