In this paper, we propose a formal method for verifying a requirement of page transitions, which is one of the most essential requirements especially for Web-based applications. The proposed method checks whether a page transition requirement is satisfied in a state transition specification of applications, such as a flowchart or an UML activity diagram, based on model checking. We applied the proposed method to real specifications of a Web application used in a certain company and found several errors including deadlock of the specifications in a short time.