A network design apparatus, a network design method, and a network design processing program design a network configuration 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 the network configuration, the optimal path candidates of each of the lines minimizing a total cost value in the overall network is calculated. In the calculation of the optimal path candidates of each of the lines, only a path candidate of each of the lines can be selected, and a combination candidate of link portion apparatuses for each of the links is derived uniquely from the selected path candidate of each of the lines.