PURPOSE: To prevent congestion in a network by allowing a network management center to collect periodically congestion information from each station, calculating route selection coefficient based on the information and allowing the station side to apply routing regulation.

CONSTITUTION: A network management center 10 inquires optional stations 100-800 about the congestion and decides the rate of selecting a route to the station to an adjacent station with respect to the congestion rate of change per unit time and the congestion of the stations 100-800 obtained for the inquiry. Then the route selection coefficient to the adjacent station of the station is sent and the route is selected based on the route selection coefficient by the adjacent station. Thus, the congestion in the network is prevented by applying the congestion control taking the entire network into account.