With the development of information and communication technology (ICT), services have often been provided through a collection of systems of various architectures interoperating with each other. System development must incorporate non-functional requirements in addition to traditional functional requirements. However, to determine the requirements of multiple cooperative systems, it is necessary a) to consider hardware architecture, user characteristics, and system safety requirements and b) to verify these at an early stage of development. UML is a well-known general purpose modeling language through which it is possible to define functional requirements and to support design and implementation efforts that are based on a specified use case model. However, it is difficult to verify such inter-system cooperation using use case models in UML. Moreover, confirming the correct behaviors, exhibited concurrently, of a system of multiple interoperating systems is difficult using the static models found in UML. This study proposes a method of transforming a model of mutually cooperating multiple systems described in UML into a model that uses the model-checking tool UPPAAL and verifying whether parallel behaviors can occur without deadlock. Consequently, a method, applied at an early stage of development, of guaranteeing the correctness of the concurrent operation and cooperation of multiple systems is demonstrated.