Abstract: The present invention discloses an authentication system and method having mobility in a public wireless LAN. The authentication system includes an access point for requesting authentication of a wireless terminal to an access point manager, enabling data transmission and reception of the authenticated wireless terminal, and requesting the access point manager to charge the wireless terminal, and the access point manager for authenticating the wireless terminal which has already been authenticated on the basis of previously-registered registration information upon the request of the access point, authenticating the wireless terminal which has not been registered through an authentication server of a wireless network operator, and transmitting the authentication information to the access point.