1. A computer implemented method performed by a computer for optimizing a structure of an industrial product, comprising: selecting a plurality of control factors from among a plurality of manufacturing parameters affecting a target characteristic of the industrial product, which is scheduled to be manufactured by a sequence of manufacturing processes, the target characteristic being at least one of a plurality of characteristics of the industrial product; setting a plurality of levels to the respective control factors; selecting a reference characteristic from among the characteristics of the industrial product; setting a reference value to the reference characteristic; selecting a prior adjustment factor affecting the reference characteristic from among the manufacturing parameters; creating conditions for a plurality of experiments assigning a plurality of combinations of the levels to the respective control factors; determining adjustment values of the prior adjustment factor to the respective experiments so that at least a part of characteristic values of the reference characteristic obtained by the experiments conforms substantially to the reference value; determining experimental characteristic values of the target characteristic corresponding to each of the experiments using the adjustment values; determining an optimal value of the target characteristic and an optimal combination of the levels based on the experimental characteristic values of the experiments, the optimal combination providing the optimal value; and generating an output signal representing the optimal value and the optimal combination; wherein the steps of selecting the plurality of control factors, setting the plurality of levels, selecting the reference characteristic, setting the reference value, selecting the prior adjustment factor, creating the conditions, determining the adjustment values, determining the experimental characteristic values, determining the optimal value and the optimal combination, and generating the output signal are performed by said computer.