The purpose of this study is to construct a prototype decision support system in product planning and designing. In this report, a model for determining a set of design alternatives is proposed to maximize the synthetic value obtained from multiple criteria, under cost constraint. An evaluation procedure of this model is presented by using both AHP and Additional Rate of Return Method for Compound Alternatives. The methods for treating dependency among criteria or alternatives are also given. The proposed model is newly characterized as a problem with multiple criteria under cost constraint.