A multiple-optical-axis photoelectric sensor system configured to detect a detection target object conveyed by a conveying device, the multiple-optical-axis photoelectric sensor system comprising: a projector comprising a plurality of light projecting units arrayed in line; an optical receiver comprising a plurality of light receiving units that are arranged so as to face the plurality of respective light projecting units; a light blocking determination unit configured to make a light blocking determination whether each of a plurality of optical axes formed between the plurality of light projecting units and the plurality of light receiving units is in a light blocking state; and a muting processor configured to temporarily disable the light blocking determination on condition that a detection signal input from an external muting instrument (A1, B1, A2, B2) changes according to a predetermined sequence, wherein the muting processor comprises: a muting start determination unit configured to start muting based on an output from the external muting instrument; and a muting determination unit configured to determine the sequence of the detection signal from the external muting instrument during the muting, by dividing the sequence into a plurality of stages, characterised in that the muting determination unit is configured to accumulate measurement information acquired in each stage, and to analyze a variation of the accumulated measurement information, and the muting processor is configured to decide an optimum range of a setting value for a muting operation condition based on an analysis result of the muting determination unit such that a predetermined condition is satisfied. a projector comprising a plurality of light projecting units arrayed in line; an optical receiver comprising a plurality of light receiving units that are arranged so as to face the plurality of respective light projecting units; a light blocking determination unit configured to make a light blocking determination whether each of a plurality of optical axes formed between the plurality of light projecting units and the plurality of light receiving units is in a light blocking state; and a muting processor configured to temporarily disable the light blocking determination on condition that a detection signal input from an external muting instrument (A1, B1, A2, B2) changes according to a predetermined sequence, wherein the muting processor comprises: a muting start determination unit configured to start muting based on an output from the external muting instrument; and a muting determination unit configured to determine the sequence of the detection signal from the external muting instrument during the muting, by dividing the sequence into a plurality of stages, characterised in that the muting determination unit is configured to accumulate measurement information acquired in each stage, and to analyze a variation of the accumulated measurement information, and the muting processor is configured to decide an optimum range of a setting value for a muting operation condition based on an analysis result of the muting determination unit such that a predetermined condition is satisfied. a muting start determination unit configured to start muting based on an output from the external muting instrument; and a muting determination unit configured to determine the sequence of the detection signal from the external muting instrument during the muting, by dividing the sequence into a plurality of stages, characterised in that the muting determination unit is configured to accumulate measurement information acquired in each stage, and to analyze a variation of the accumulated measurement information, and the muting processor is configured to decide an optimum range of a setting value for a muting operation condition based on an analysis result of the muting determination unit such that a predetermined condition is satisfied.