Method and apparatus for communication between client and service provider using external server, and a method and apparatus for controlling communication between a client and a service provider are provided. The method includes: receiving from the service provider a first authentication token indicating that the service provider has authenticated communication with the client by logging on the service provider; storing, in the external server, authentication information containing the first authentication token and additional information relating to communication with the service provider; receiving, when there is a request to access the service provider, authentication information corresponding to the request from the external server; and communicating with the service provider using the received authentication information. It is possible to alleviate the burden on a user to enter his or her ID and password, and to remove necessity for a user to enter the ID and password after registration has been performed once.