Accommodation design for wavelength and sub-λ paths in a communication network is performed. If sub-λ path accommodation is possible according to search for a wavelength path present in a single-hop logical route, the accommodation in the wavelength path is executed. If sub-λ path accommodation is possible according to search for a wavelength path present in a multi-hop logical route, a logical route is selected based on the wavelength path and the sub-λ path is accommodated in the wavelength path. Additionally, each physical route suitable for the sub-λ path accommodation is searched for. If the route can accommodate a wavelength path set in a single-hop logical route by available wavelength allocation, the sub-λ path is accommodated in the wavelength path. Furthermore, routes in consideration of overlapping of nodes, pipelines, and links and operation rate are selected based on information about the start and end nodes of each of redundant routes.