The cellular phone ownership rate continues to increase, meaning one person may now own two or more. Meanwhile, a lot of terminals that receive cellular phone services through a mass broadband communication network are being commercialized. When service is received through the cellular phone, the mobile network operator authenticates the subscriber. However, service providers other than the mobile network operators provide communication services and other services through fixed networks. In this situation, if we can use the subscriber authentication that the mobile network operator provide for the fixed network service, fixed mobile convergence (FMC) will be achieved and mobile network operators will be able to better prevent unauthorized users from using their services. In addition, services will become more convenient because users will be authenticated by swiping one cellular phone when switching from using a fixed terminal to another fixed terminal. A mechanism has been developed that allows mobile network operator to authenticate their subscribers' account when using a terminal connected to a fixed network. In addition, services can be easily switched between fixed terminals by using the proposed mechanism. Moreover, a system is constructed on the basis of the proposed mechanism, and its performance is evaluated.