In Service Engineering, a design methodology of services based on customer requirements has been proposed. However, due to the fact that customer wants and needs are becoming further diversified, it is still difficult to establish a design method to customize a service to satisfy various customer requirements concurrently. "Mass-Customization" is an effective way to solve the problem. The purpose of this study is to propose a design method to realize Mass-Customization of services. In this paper, case analysis is conducted to clarify structural characteristics of Mass-Customized services.