An economical optical network is constituted by effectively using network resources by using the minimum number of, or minimum capacity of 3R repeaters. An optical node device stores a value Q, preset for each link based on optical signal deterioration characteristics in a link between the optical node device itself and an adjacent node. When the optical node device itself is a source node, the optical node device transmits an initial value P of a minuend to a next hop adjacent optical node device. When the optical node device itself receives from a previous hop adjacent optical node device, the initial value P or a minuend value P', which has already been reduced from the initial value P, the optical node device calculates (P-Q) or (P'-Q). The optical node device compares a calculated result with a threshold value. If the calculated result is greater than the threshold value, the optical node device transmits the calculated result to the next hop adjacent optical node device. If the calculated result is less than or equal to the threshold value, the optical node device implements 3R relay of an optical signal that reaches the optical node device itself. When the optical node device itself is not the destination node of an optical path to which the value of the minuend is transmitted, the optical node device transmits the initial value P of the minuend to the next hop adjacent optical node device using the optical node device itself as a 3R source node.