In a gateway system for connecting a telephone network utilizing a common channel signaling system No. 7 to an IP (Internet Protocol) network, the gateway system includes a media gateway and a media gateway controller group including a plurality of media gateway controllers which are assigned a common point code. Any one of the media gateway controllers is for terminating a No. 7 signal representative of a control signal of the common channel signaling system No. 7 in the telephone network and for carrying out call control and connection control to the IP network by controlling the media gateway through the IP network so that a communication path is established between the telephone network and the media gateway. Each of the media gateway controllers comprises a No. 7 signal processing portion for terminating the No. 7 signal and a call processing control portion for carrying out the call control and the connection control to the IP network by controlling the media gateway through the IP network so that the communication path is established between the telephone network and the media gateway. The No. 7 signal processing portion and the call processing control portion have a M3UA (SS7 (Signaling System No. 7) MTP3-User Adaptation Layer) function.