[Subject] In a distributed authentication system, if a terminal including a plurality of communication devices changes a communication device to another communication device during using a service, the service under use can be used in succession, and the number of times for execution by the user can reduced.[Solving Means] An authentication-information management unit (5) registers authentication information of the user authenticated by each authentication unit (4), and allows sharing of said authentication information. A session-information management device (24) of a service providing unit (2) manages session information including a session identifier of a session established between the same and the terminal unit (3). More specifically, the service providing unit 2 performs individualized management of sessions established between the same and the terminal unit (3). The session-information management device (24) achieves a continuous provision of the service by authorization of provision of the service to the terminal unit (3) based on the individualized management of said session information.