To quantitatively judge the presence/absence of the occurrence of wrinkles.

When the pressing simulation of a plate stock is effected based on an elasto-plastic finite element method using a computer, and the occurrence of wrinkles is predicated based on the calculation result, the equivalent stress and the equivalent strain in each element for unit time in the pressing simulation are outputted in the pressing process of the stock. The difference between the equivalent stress obtained from a work-hardening curve of the stock and the outputted equivalent stress is obtained as a wrinkle evaluation parameter relative to the outputted equivalent strain, and the presence/absence of the occurrence of wrinkles is judged based on the value of the wrinkle evaluation parameter.