PURPOSE: To improve the operating efficiency of a network by updating the routing information at a required case only in a network system, and avoiding a periodic broadcast of routing information.

CONSTITUTION: An update request section 31 publicating an update request of routing information is provided to a node 3 in the network system. In response to the publication of the update request from the update request section 31, the routing information possessed by the route management device 1 and the node 3 is updated. Thus, the periodic broadcast of the routing information is avoided and only when the update is required, it is implemented. Thus, the rate of the communication as to the routing information occupied by the entire communication is reduced to improve the operating efficiency of the network.