1. A network configuration management apparatus, comprising: a selecting section that selects two of a plurality of network devices which are connected to a network; a route acquiring section that acquires a communication route between the two network devices selected by the selecting section; a shortest distance computing section that computes a number of links from each of the network devices to each of the other network devices on the communication route, to determine a smallest value of the number of links for each of the network devices; a route relation degree determining section that determines a degree of route relation for each of the network devices as 
 X= 1/(1+ m ) where X is the degree of route relation and m is the smallest value of the number of links; and a degree of importance determining section that determines a degree of importance of each of the network devices as 
 imp =exp{ k ( X −μ)/σ} where imp is the degree importance, k is a degree of importance parameter, μ is an average of the degree of route relation for the network devices, and σ is a standard deviation of the degree of route relation for the network devices.