This paper deals with a design optimization process with some experiments that are often executed in design and development phase. In order to avoid repetition of experiments as possible, Taguchi method has been proposed from a view point of robustness. And, Nakazawa method has been proposed from a view point of optimal balance among multi-required specifications. However, these methods have not been used together in practical engineering fields although both methods commonly use the orthogonal array in the experimental design. There are rare studies of combinational use to make the most of characteristic points of the both methods. In this paper, the characteristic points of these methods are examined and arranged first. Then, an efficient combinational use of these methods is proposed. A simple case study shows that the proposed method is useful for practical design and development processes.