A photo detecting circuit using a photo detecting device, comprising: a timing generator for generating a timing signal; and a power supply for applying a reverse-bias voltage pulse to the photo detecting device according to the timing signal; characterized by comprising: a mask generator for generating a pulse noise mask signal having two mask portions having each a time width for eliminating two pulse noises respectively based on the timing signal, wherein the two pulse noises appear in a differential waveform due to parasitic capacitance of the photo detecting device at two timings corresponding respectively to the rising and trailing edges of the reverse-bias voltage pulse; and a pulse noise eliminator for eliminating the two pulse noises from an output signal of the photo detecting device by using the two mask portions of the pulse noise mask signal to mask the two pulse noises, respectively, to produce a photo reception signal, wherein the mask generator delays the timing signal by a predetermined delay time to produce a delayed timing signal and generates the two mask portions of the pulse noise mask signal from a logical combination of the timing signal and the delayed timing signal, wherein the predetermined delay time is equivalent to a time width of each of the mask portions. a timing generator for generating a timing signal; and a power supply for applying a reverse-bias voltage pulse to the photo detecting device according to the timing signal; characterized by comprising: a mask generator for generating a pulse noise mask signal having two mask portions having each a time width for eliminating two pulse noises respectively based on the timing signal, wherein the two pulse noises appear in a differential waveform due to parasitic capacitance of the photo detecting device at two timings corresponding respectively to the rising and trailing edges of the reverse-bias voltage pulse; and a pulse noise eliminator for eliminating the two pulse noises from an output signal of the photo detecting device by using the two mask portions of the pulse noise mask signal to mask the two pulse noises, respectively, to produce a photo reception signal, a mask generator for generating a pulse noise mask signal having two mask portions having each a time width for eliminating two pulse noises respectively based on the timing signal, wherein the two pulse noises appear in a differential waveform due to parasitic capacitance of the photo detecting device at two timings corresponding respectively to the rising and trailing edges of the reverse-bias voltage pulse; and a pulse noise eliminator for eliminating the two pulse noises from an output signal of the photo detecting device by using the two mask portions of the pulse noise mask signal to mask the two pulse noises, respectively, to produce a photo reception signal, wherein the mask generator delays the timing signal by a predetermined delay time to produce a delayed timing signal and generates the two mask portions of the pulse noise mask signal from a logical combination of the timing signal and the delayed timing signal, wherein the predetermined delay time is equivalent to a time width of each of the mask portions.