An optical receiver comprising: first combining means (13, 21, 23) for outputting first combined light by combining local light of first polarization and signal light of second polarization that is orthogonal to the first polarization; first conversion means for converting the first combined light to a first electric signal; first polarization means for allowing a component of polarization plane having an angle of 45 degrees relative to each of polarization planes of the first polarization and the second polarization to pass through; second conversion means for converting a component of the first combined light that has passed through the first polarization means to a second electric signal; first delay means for delaying light of the first polarization or the second polarization by 1/4 wavelength; second polarization means for allowing a component of polarization plane having an angle of 45 degrees relative to each of polarization planes of the first polarization and the second polarization to pass through; third conversion means for converting a component of the first combined light that has passed through the first delay means and the second polarization means to a third electric signal; branching means for outputting a fourth electric signal and a fifth electric signal by branching the first electric signal; first subtraction means for subtracting the fourth electric signal from the second electric signal; and second subtraction means for subtracting the fifth electric signal from the third electric signal; wherein the first combining means (13, 21, 23) is configured to output the first combined light to each of the first conversion means, the first polarization means, and the first delay means. first combining means (13, 21, 23) for outputting first combined light by combining local light of first polarization and signal light of second polarization that is orthogonal to the first polarization; first conversion means for converting the first combined light to a first electric signal; first polarization means for allowing a component of polarization plane having an angle of 45 degrees relative to each of polarization planes of the first polarization and the second polarization to pass through; second conversion means for converting a component of the first combined light that has passed through the first polarization means to a second electric signal; first delay means for delaying light of the first polarization or the second polarization by 1/4 wavelength; second polarization means for allowing a component of polarization plane having an angle of 45 degrees relative to each of polarization planes of the first polarization and the second polarization to pass through; third conversion means for converting a component of the first combined light that has passed through the first delay means and the second polarization means to a third electric signal; branching means for outputting a fourth electric signal and a fifth electric signal by branching the first electric signal; first subtraction means for subtracting the fourth electric signal from the second electric signal; and second subtraction means for subtracting the fifth electric signal from the third electric signal; wherein the first combining means (13, 21, 23) is configured to output the first combined light to each of the first conversion means, the first polarization means, and the first delay means.