A network system includes a plurality of individual Internet service providers each having access points, and a parallel Internet service provider connected to the plurality of individual Internet service providers, the individual Internet service providers and the parallel Internet service provider each include an authentication server. When the access point of a provider receives a connection request from a user who contracts with the parallel service provider, the provider transfers a connection ID and a password to an authentication server of the parallel Internet service provider to perform user authentication. When a result of the authentication is good, the user terminal is connected to the user terminal through the access point.