To provide an audio gateway device capable of improving expansibility and flexibility of a numbering system of audio networks.

A VoIP call control signal is reported from a VoIP trunk card 31 through a VoIP trunk control part 32 to a VoIP call control signal analytic part 33, and call information such as caller information, callee information, and the like contained in the call control signal is analyzed and held in a call information storage part 34. An ISDN layer 3 message creating part 35 creates a call setting message from the held information, and a call originating node information mapping part 35a reads call originating node IP address information out of the call information storage part 34, contains it in the ISDN layer 3 message as call originating subaddress information and sends it from an ISDN trunk control part 36 through an ISDN trunk card 37 to an ISDN circuit switched network 200 as a call setting message.