To solve three problems of the quick construction of a spanning tree (1), the averaging of load of a network resources (2) and the efficient acquisition of routing information to nodes existing in different rings (3) in a routing bridge system connecting respective rings by a bridge.

A node for determining a data transmission route by using an address of a data link layer is provided with a node tree preparation part for preparing a spanning tree between rings, a node DB and a ring DB for recording an optimum transmission direction and cost of respective nodes existing in each ring and that of respective rings, and a transmitting direction determination part for determining the transfer destination of received data by using the node DB, the ring DB or the inter-node spanning tree and the inter-ring spanning tree in accordance with the sort of the destination.