A light receiving circuit includes: a 1-bit delay interferometer; two photodiodes; and a demodulating circuit for converting current signals of the photodiodes into voltages to thereby demodulate signals that have been modulated by return-to-zero differential phase shift keying, the demodulating circuit including a differential transimpedance amplifier, in which the differential transimpedance amplifier includes a level adjusting circuit that has a function of adjusting levels of a positive phase signal and a negative phase signal of two feedback closed loops.