A caller identification system provides a caller identifier of an actual user rather than the conventional telephone number dependent on a caller terminal. Further, a caller base billing method and its system can bill an actual user by carrying out user authentication through a certification authority for a caller identifier that is independent of a caller terminal. The method includes the steps of receiving authentication information of the caller from a caller terminal; verifying the authentication information; and carrying out call setup if the authentication information and the certificate match, wherein the authentication information is generated by using a caller identifier and a private key that are applied by the caller, with no dependency on the caller terminal, and caller information corresponding to the caller identifier is transmitted to a callee terminal during call setup.