A system and method of managing multiple identities using a multiple identity management system includes receiving a user authentication signal from a user terminal, transmitting the user authentication signal to a first service server, the first service server matching the user authentication signal with a particular user ID associated with the first service server, receiving an authorization signal corresponding to the user authentication signal from the first service server, transmitting the authorization signal to the user terminal, receiving a request for validation of a user identification number corresponding to the authorization signal from a second service server, the second service server receiving the authorization signal transmitted via a user input from the user terminal, and transmitting the user identification number corresponding to the authorization signal to the second service server.