A branch units branches an optical signal by the number of wavelength intervals. Each band division unit generates a band division signal in which a signal band is divided into N division bands and an odd channel and an even channel are separated from each other. Multiplexing units multiplex band division signals of the same signal band, and branch means output the multiplexed signal to an optical receiver. A control unit controls the wavelength selective switch included in the band division units based on information indicating a signal arrangement of the signals in the respective wavelength intervals, thereby causing a signal of a signal band in which a signal of a corresponding wavelength interval is present to be included in each band division signal.