A network management server stores, in terms of a transmission path within the network, each occurrence pattern of a failure occurrence area in which a failure has occurred in a communication apparatus through which the transmission path passes. Information for identifying a recovery plane serving as a set of recovery paths corresponding to each occurrence pattern and information for identifying the communication apparatus through which each of the recovery paths passes is also stored. When a failure occurs in any one of the plurality of areas, whether or not the failure corresponds to any one of the failure occurrence patterns, the information for identifying the recovery plane corresponding to the identified failure occurrence patterns is acquired; and the communication apparatus through which each of the recovery paths included in the recovery plane passes is notified of the information for identifying the recovery plane acquired.