We propose a hierarchical optical path network design algorithm. In order to efficiently accommodate wavelength paths in each waveband path, we define a source-destination Cartesian product space that allows the 'closeness' among wavelength paths to be assessed. By grouping 'close' wavelength paths, found by searching for clusters in the space, we iteratively create waveband paths that efficiently accommodate the wavelength paths. Numerical experiments demonstrate that the proposed algorithm offers lower total network cost than the conventional algorithms. The results also show that the hierarchical optical path network is effective even when traffic demand is relatively small.