We propose a product design optimization method that maximizes the integrated satisfaction level for evaluative factors. Product designs include many evaluative factors that have complex interrelationships. To cope with such circumstances, we construct strategies and a practical method to obtain optimum design solutions. First, the evaluative items for the product are listed and each item is decomposed into evaluative factors. Next, to express designers' or potential customers' levels of satisfaction for the characteristic values of each evaluative factor, we define satisfaction functions that incorporate the relationship between characteristic values and satisfaction levels. Weighting coefficients for the evaluative factors are then obtained by the pair comparison method. Finally, an integrated satisfaction level is formulated by summing the characteristic values with their weighting coefficients over the entire set of evaluative factors. The integrated satisfaction level of the objective function is maximized, and optimum design solutions with maximum satisfaction levels are then obtained. If necessary, these solutions can be modified and improved by re-examining and adjusting the satisfaction functions and weighting coefficients. Furthermore, the proposed method can be used to find schemes that improve the integrated satisfaction level. The utility of the proposed method is demonstrated using a passenger train coach design.