The VoIP gateway in accordance with the present invention serves to send a connection request to either the IP network or the PSTN on the basis of the information stored in the VOIP gateway and the destination telephone number contained in the connection request as sent from the telephone terminal. Also, even if a connection request is decided to be sent to the IP network, the VOIP gateway sends the connection request to the PSTN when the IP network state judgment unit judges that the communication through the IP network is impossible. Furthermore, if a destination telephone number includes predetermined identification information, the VOIP gateway can forcibly send the connection request to the PSTN.