Method and apparatus for offering certification service

A method and an apparatus for offering an integral authentication service are provided to compare an authentication number including a service interface with an authentication that a subscriber inputs to authenticate the subscriber, thereby effectively protecting personal information when the subscriber subscribes to a member of a web site. An open type gateway(130) is connected to an internet. The open type gateway transmits a service interface including an authentication number. An authentication server(140) stores information of an authentication service subscriber. If a subscriber authentication request is received from a web site server(180), the authentication server requests service interface transmission to the open type gateway through an internet. If the authentication number included in the transmitted service interface is matched with the authentication number which the subscriber inputs, the authentication server extracts the stored authentication service subscriber information and transmits the information to the web site server. A communication company server(160) is connected to the open type gateway.