A VoIP gateway system for use in the IP network comprises a plurality of voice processing units, each having a unique IP address and a main processing unit connected via a HUB. The voice processing units and the main processing unit share the local LAN for sending and receiving a voice data packet by connecting the PSTN and the IP network. The load concentration on the system bus is reduced, thus effectively increasing the number of lines which can be handled for one voice processing unit. When transferring a packet to the IP network, only the IP address of the main processing unit is managed by the gatekeeper, thus effectively performing the IP address management at the gatekeeper.