There are many kinds of networks in vehicle for their purposes. In-vehicle networks, however, are not unified to single network. The networks are composed of several local networks because of communication speed, cost and efficiency. Because the complexity of network design for communication increases, local networks need a framework for interworking between heterogeneous networks. In this paper, a framework interworking between in-vehicle networks for ITS(Intelligent Transportation System) is proposed and implemented. The proposed framework consists of a compatible protocol, message conversion module, message transceiver module and message analysis module. The results obtained by implementation show that the framework efficiently supports the communication of information between heterogeneous in-vehicle networks.