To enhance the efficiency of a process for determining the specifications of a mold used in the injection molding of a resin.

Molding simulation including flow analysis is performed (S14) on the basis of an initially set or altered sheet thickness, the arrangement of a resin filling gate and a gate size (S12). Then, data conversion is performed with respect to the result of the molding simulation if necessary (S16) to evaluate molding quality (S18). In the evaluation of molding quality, it is judged whether a molding restricting condition related to welding or an air trap is satisfied. When an optimizing process is not completed, operation is performed according to optimizing algorithm (S22). In order to searching mold specifications for satisfying the molding restricting condition and minimizing the weight of a molded product, a set condition is altered (S12). The above mentioned processes are repeated a predetermined number of times or until satisfying a converging condition to determine the mold specifications.