To select a route for a correct destination even when a link in the mid way becomes unusable by constituting a virtual communication network where the unusable link is eliminated from topology information of a communication network and selecting the shortest route when an edge node of a transmission terminal prepares route information.

When a link becomes unusable, its information is made to be reflected upon topology information of a reproduced virtual communication network in a virtual communication network construction part 23 of each of communication nodes A to L by having a use able/disable notification part 22 mutually notify the information between the communication nodes A to L. Then, in accordance with such a piece of information that certain links are unusable as this way, a route selection part 24 of the communication node A selects the shortest route to a specified communication node from the communication node A to a specified communication node faced on the topology information of the virtual communication network from which those unusable links are removed. A specified route information generation part 25 of the communication node A prepares specified route information.