An optical transport network system includes a plurality of NEs, each transmitting wavelength-multiplexed optical signals. Each NE includes a routing information DB that is used to store reachable area information, which contains identifiers of other NEs in a range within which the optical signals can be transmitted from the own NE without using an REG. A FROM NE includes a path candidate searching unit that searches for a plurality of path candidates for transmitting optical signals from the FROM NE to a TO NE. The TO NE includes a path selecting unit that selects a path for transmitting optical signals from among a plurality of path candidates. The path selecting unit obtains the number of times for which the REG is used for each of the plurality of path candidates; and, based on each number of times that is obtained, selects a path for transmitting the optical signals.