In an IP (Internet Protocol) gateway apparatus for storing a plurality of channels, voice signals supplied from the respective channels are packeted, and then the voice packets are sent out to an IP network. The IP gateway apparatus is provided with a synchronization timing generating apparatus for outputting a synchronization signal indicative of timing at which the voice signals of the respective channels are packeted, and a packeting apparatus for packeting the voice signals supplied from the respective channels in accordance with the synchronization signal outputted from the synchronization timing generating apparatus to thereby send out the voice packets to the IP network.