A distance calculating unit includes a first filter that receives a detection signal of reference pulsed light, a second filter that receives a detection signal of measuring pulsed light, an adder circuit that adds the outputs from the two filters together, an A/D converter that receives the output signal from the adder circuit, and a separated-signal calculating unit that analyzes the output from the A/D converter and that generates a first separated signal corresponding to a reference detection signal and a second separated signal corresponding to a measurement detection signal. The distance calculating unit further includes a conversion processing unit that converts the phase of at least one of the two separated signals into a phase of a predetermined frequency, and a distance calculating unit that calculates a distance to an object by using a phase difference between the two separated signals in the predetermined frequency.