Recently, a method which enables to efficiently and stably develop a huge system as the combination of services such as cloud computing is needed. In such development, requirements analysts must understand the specification of existing services because it requires creating services by using the combination of services including existing services. To achieve this purpose, we have proposed a method of model-driven requirements analysis using unified modeling language (UML). The main feature of the proposed method is to automatically generate a Web user interface (UI) prototype from UML requirements analysis model (RA model) so that the requirements analysts can easily and efficiently validate the RA model which separately and concretely define the behavior and structure by using UML activity diagrams, a UML class diagram and UML object diagrams. In this paper, we evaluate the effectiveness of the proposed method from the viewpoint of whether the proposed method enhances the traceability between the requirements specification and final product through a case study. In the case study, we measure problems such as ambiguity and inconsistency of the specification by redefining of informal specification which is defined by an actual enterprise along its regular steps of the software development by using the proposed method.