An optical relay device is provided which is capable of outputting control signal light without equipping a light source for the control signal light and capable of flexibly managing and changing a wavelength of the control signal light in accordance with a state of a network. The optical relay device includes an optical receiving unit that receives a wavelength multiplexed optical signal, a control unit that specifies a first wavelength and outputting notification information, and a processing unit that selects an optical signal having the first wavelength from the received wavelength multiplexed optical signal, applying intensity-modulation in accordance with the notification information to the selected optical signal, adding the intensity-modulated optical signal back to the wavelength multiplexed optical signal, and outputting the wavelength multiplexed optical signal.