In Service Engineering, a design methodology of services based on customer requirements is 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.