An optical transmission device that is installed at a node of a network and that performs transmission of an optical signal transmits the optical signal to an optical transmission device at the next node without amplifying the optical signal. The optical transmission device generates an adjustment optical signal used by a reception-side optical amplifier in the optical transmission device at the next node to adjust gain for a transmission loss of the optical signal. At the time of booting of the optical transmission device, the optical transmission device transmits the generated adjustment optical signal to the reception-side optical amplifier in the optical transmission device at the next node. Upon receiving a gain-adjustment-completion signal for notifying completion of gain adjustment using the adjustment optical signal from the reception-side optical amplifier, the optical transmission device controls the transmission of the adjustment optical signal to be stopped.