Use case diagrams appear in early steps of a UML-based de- velopment. They capture user requirements, structured by the concepts of use cases and actors. An admitted good modeling practice is to de- sign simple, easy-to-read use case diagrams. That can be achieved by introducing relevant generalizations of actors and use cases. The paper proposes an approach based on Formal Concept Analysis and one of its variants, Relational Concept Analysis, to refactor a use case diagram as a whole in order to make it clearer. We developed a tool and studied the results on about twenty examples, concluding on the relevancy of the approach on our benchmark.