Enterprise information systems take many forms, one of which is Web applications. The demand for rapid development of such Web applications is becoming stronger, but there is still no good way. Round-trip engineering is a software development method that iterates between the modeling phase and coding phase, allowing for iterative and incremental development. However conventional tools only support static models such as class diagrams. We thus propose a tool for round-trip engineering of Web applications that supports dynamic models such as sequence diagrams and statecharts. We introduce a navigation model to model the navigation between Web pages. This model is used to link the various diagrams as well as to generate source code. We describe a case study to show the effectiveness of our tool.