PROBLEM TO BE SOLVED: To provide a working condition setting method for reducing working errors in a case where an amount of working errors can be detected, but a direction of them cannot be detected.SOLUTION: There is provided a method for setting a working condition for a case where it is possible to quantitatively calculate a working error generated when a product having a common property is worked, but not possible to detect a direction of the error. For example, a case is assumed where a prism error of an astigmatic single vision (SV) spectacle lens as a product is reduced as a working error. When for example 1500 lenses are worked, the working condition is changed intentionally such that a 0.05 pupillary distance (PD) base-in prism is added to each of one third of the lenses, and a 0.05 PD base-out prism is added to each of another one third of the lenses. An inclination error and a position error which are generated in working can be analysed by performing regression analysis for each lens group, resul
