To provide an FM signal optical receiver capable of suppressing distortion caused by the distortion of phases in transmission.

An FM optical signal inputted into an optical receiver 2013 from an optical fiber cable 92 is inputted into an optical fiber grating 2011 via an optical circulator 2010 placed in an optical/electrical converter 2015. After the optical signal has been converted into an electrical signal by an optical/electrical converter 2016 comprising a photodiode or an avalanche photodiode and a preamplifier 2017, the converted signal is inputted into a limiter amplifier 2018, a branching element 2019, a delay circuit 2020, a mixer 2021, and a low-pass filter 2022. At this stage, the signal is amplified to predetermined signal intensity and demodulated to an original AM signal 21.