An optical range finder has a projection unit for projecting optical flux to an object, a photoreceiving unit for receiving the optical flux returned from the object and outputting a detection signal in accordance with a light quantity of the received optical flux, and a circuitry unit for conducting a measurement of a distance to the object based on the detection signal. In the circuitry unit, a light quantity determination circuit compares a signal level of the detection signal with a reference level to carry out binary determination of the light quantity of the returned optical flux. A reference level setting circuit switchably supplies a plurality of reference levels to the light quantity determination circuit, the reference levels being preset in correspondence to multiple stages of the distance. A control circuit controls the reference level setting circuit to supply the reference levels while switching the reference levels so as to enable the light quantity determination circuit to execute a plurality of the binary determination with the supplied reference levels for one measurement, thereby specifying the distance to one of the multiple stages based on the thus obtained plurality of the binary determination.