A receiving device includes a light source outputting local oscillation light, a detector detecting intermittent input of a burst light signal by using the local oscillation light, a first converter converting the detected burst optical signal into an electrical analog signal, an amplifier amplifying the analog signal according to a gain, a second converter converting the amplified analog signal into a digital signal, and a setting processor setting the gain of the amplifier and a wavelength of the local oscillation light instructed by a control device when setting a communication line with one of transmitting devices transmitting the burst optical signal, wherein, before setting the communication line, the setting processor switches the wavelength of the local oscillation light according to the burst optical signal transmitted from each of the transmitting devices, adjusts the gain of the amplifier and notifies the control device of the adjusted gain.