An orthogonal cross-polarization interference compensating device, which compensates for orthogonal cross-polarization interference of a first polarization signal with a second polarization signal, comprising: an orthogonal cross-polarization interference compensator that receives the second polarization signal and generates a compensation signal for compensating phase noise included in the first polarization signal based on the received second polarization signal; a demodulator that receives the first polarization signal and the generated compensation signal, compensates for the orthogonal cross-polarization interference by suppressing phase noise included in the received first polarization signal based on the received compensation signal, and outputs a compensated first polarization signal as a demodulation signal; an error detector that generates an error signal indicating phase difference between the first polarization signal compensated by the demodulator and a proper first polarization signal; a phase detector that generates a differential signal indicating phase difference between the first polarization signal and the second polarization signal based on the generated compensation signal and the generated error signal; an integrator that generates an integration signal by integrating the differential signal generated by the phase detector; a shifter that adjusts the compensation signal based on the integration signal generated by the integrator; and a controller that determines whether or not the orthogonal cross-polarization interference is present based on the compensation signal adjusted by the shifter, and if no orthogonal cross-polarization interference is present, adjusts an integration value indicated by the integration signal to zero. an orthogonal cross-polarization interference compensator that receives the second polarization signal and generates a compensation signal for compensating phase noise included in the first polarization signal based on the received second polarization signal; a demodulator that receives the first polarization signal and the generated compensation signal, compensates for the orthogonal cross-polarization interference by suppressing phase noise included in the received first polarization signal based on the received compensation signal, and outputs a compensated first polarization signal as a demodulation signal; an error detector that generates an error signal indicating phase difference between the first polarization signal compensated by the demodulator and a proper first polarization signal; a phase detector that generates a differential signal indicating phase difference between the first polarization signal and the second polarization signal based on the generated compensation signal and the generated error signal; an integrator that generates an integration signal by integrating the differential signal generated by the phase detector; a shifter that adjusts the compensation signal based on the integration signal generated by the integrator; and a controller that determines whether or not the orthogonal cross-polarization interference is present based on the compensation signal adjusted by the shifter, and if no orthogonal cross-polarization interference is present, adjusts an integration value indicated by the integration signal to zero.