To provide a gateway apparatus where an information terminal inside a LAN can conduct communication with other apparatuses in the LAN and an apparatus outside the LAN, at the same time.

The gateway apparatus includes a storage section for storing local area addresses that are addresses utilized in the local area network (LAN); and a control section that reads the local area address of an information terminal from the storage section and transmits the local area address to the information terminal, when receiving a terminal authentication request signal including information of requesting the address from the information terminal connected to the local area network, and transmits a user authentication request signal to an authentication server and transmits an external address that is an external network address received from the authentication server to an information terminal, when the local area address is set to an outgoing address and the gateway apparatus receives the user authentication request signal, including information of requesting an address to the authentication server of the external network from the information terminal.