To perform optimal control of a DPSK (differential-phase-shift-keying) demodulation circuit in accordance with the center wavelength of a DPSK optical signal.

A DPSK optical receiver includes a DPSK demodulation circuit 3, an optical bandpass filter 7, a photodetector 10, and a control circuit 11. The DPSK demodulation circuit 3 demodulates a DPSK optical signal. The optical bandpass filter 7 extracts an optical signal near the center wavelength from the DPSK optical signal and extracts a demodulated optical signal neat the center wavelength from a DPSK demodulated optical signal output from the DPSK demodulation circuit 3. The photodetector 10 detects the optical power level of the DPSK demodulated optical signal extracted by the optical bandpass filter 7. The control circuit 11 performs phase control on the DPSK demodulation circuit 3 so as to optimize the DPSK demodulation circuit 3 with respect to the center wavelength of the DPSK optical signal on the basis of the optical power level detected by the photodetector 10.