With a network design apparatus, a network design method, and a network design processing program, a network configuration is designed for a network in which a transfer apparatus is disposed at each of a plurality of communication hubs and the communication hubs are connected via a link by a link portion apparatus in the transfer apparatus. In design of a network configuration, a threshold value of an inter-end delay and the number of redundant paths are calculated for each line on the basis of topology information, line information, and design parameter information. A path candidate set is calculated for each line on the basis of the threshold value of the inter-end delay and the number of redundant paths.