To provide an optical network capable of preventing path setting by signaling from being failed due to apparatus constraints through the efficient utilization of wavelength resources and to provide a distributing routing control method used for the optical network.

A routing function 112 acquires link information including available wavelength information from a link management function 111. The routing function 112 uses the routing protocol to exchange the link information with adjacent nodes to collect the link information of all nodes on a network. A signaling function 114 requests a routing calculation function 113 to calculate routing from its own node to a node and an available wavelength. The routing calculation function 113 calculates the routing reachable to a node from its own node on the basis of the link information acquired from the routing function 112. The signaling function 114 uses the signaling protocol and sets an optical path along the routing calculated by the routing calculation function 113.