PURPOSE: To obtain a distance detecting device having no moving part, which is capable of coping with a variation of base line length by a simple adjustment, by providing a means for varying a compared reference level of a circuit for quantizing and A/D-converting a distance detecting output, in a distance detecting system which utilizes triangular surveying.

CONSTITUTION: An output VoD' of a difference detecting circuit 8 is decided by a distance l to an object to be photographed 4, a distance (f) between a photodetecting lens 5 and a semiconductor light position detector (PSD) 2, overall length C of the PSD 2, base line length S, etc. To a non-inverted input terminal of comparators CaWCd of an A/D converting circuit 9, a voltage VoD' corresponding to the distance l is applied, and it is compared with compared reference voltage applied to an inverted input terminal. The compared reference voltage is decided by an output current Iref of a current source 9a, and resistances RaWRd. In a displaying circuit 10, one of light emitting diodes L1WL5 is lighted in accordance with a distance 1 of an object to be photographed. By varying the current value Iref of the current source 9a, adjustment against a variation of the base line length S is executed.