Today, developing various types of products in a short design lead-time is needed to satisfy consumers' needs. In this study, a method to support expansion of design requirements using product cases is proposed. Previously, framework for expansion of design requirements was proposed and a supporting system was developed based on the framework. In this paper, first, a result of experiments using ... [Show full abstract] the systems was shown. While the result shows the potential of the system, the result also clarified the problem regarding the efficiency of the system. Then, a method to find implicit evaluation criterion using by the designer was proposed, and the extraction process of the system was extended considering implicit evaluation criteria. Finally, case studies and experiments were done using the system. The results show that the extended system can extract the design requirements effectively.