Designing a signage system in complex and large-scale facilities such as airport passenger terminals, stations or shopping malls has a significant impact on usability of the facilities. Facility managers would like to provide appropriate guidance information to facility users by using a signage system. It is difficult, however, to create the signage system designed to provide the right information to various types of users in the right place at the right timing. This paper focuses on an airport terminal and develops an agent-based model that represents the behavioral characteristics of passengers and the essential features of signs. The simulation with the model can show possible passenger behaviors and congestion situations in the facility under many different types of signage systems. As the results, we can support the managers' decision to build the signage system before it is actually implemented.