Abstract: An IP communication interface device includes first and second connecting units, and first, second and third processors. The first processor coding first media data as B-channel data inputted to the first connecting unit from a circuit switched network, decoding packet-disassembled media data into which a packet of second media data inputted to the second connecting unit from a LAN is disassembled, and transmitting the decoded media data to the first connecting unit for forwarding as the first media data to the circuit switched network. The second processor packetizing first coded media data, disassembling the packer of the second media data, and transmitting as packet-disassembled media data to the first processor.