A photoelectric sensor comprising: a light projecting part configured to project light for detection; a light-receiving part configured to perform light-receiving processing according to a light projecting operation; a detector configured to perform object detection processing by comparing a received light amount to a threshold previously-stored; and a manipulation part configured to be used in a setting manipulation, wherein the manipulation part comprises one switch configured to receive a manipulation corresponding to one of a plurality of tunings, wherein the plurality of tunings defined for each intended purpose of the photoelectric sensor are determined according to how the one switch is manipulated by a user, wherein the manipulation corresponding to the one of the plurality of tunings is performed to issue an instruction to measure the received light amount used for setting the threshold by: determining a reference received light amount, the reference received light amount being used to set the threshold based on the received light amount measured according to a determination criterion, the determination criterion being defined by how the one switch is manipulated by the user; and performing sensitivity adjustment of the photoelectric sensor in order to set the reference received light amount to a value suitable for the setting of the threshold characterized in that the photoelectric sensor further comprises a display part that is configured to: indicate a character string that represents the number of times the one switch is being manipulated; indicate a character string that represents the one of the plurality of tunings determined by how the one switch is manipulated by the user; indicate by switching an indicating lamp from a lighting state to a blinking state when the one switch is continuously pressed for three seconds; and display the threshold, which is fixed based on the reference received light amount, together with the received light amount after sensitivity is adjusted a light projecting part configured to project light for detection; a light-receiving part configured to perform light-receiving processing according to a light projecting operation; a detector configured to perform object detection processing by comparing a received light amount to a threshold previously-stored; and a manipulation part configured to be used in a setting manipulation, wherein the manipulation part comprises one switch configured to receive a manipulation corresponding to one of a plurality of tunings, wherein the plurality of tunings defined for each intended purpose of the photoelectric sensor are determined according to how the one switch is manipulated by a user, wherein the manipulation corresponding to the one of the plurality of tunings is performed to issue an instruction to measure the received light amount used for setting the threshold by: determining a reference received light amount, the reference received light amount being used to set the threshold based on the received light amount measured according to a determination criterion, the determination criterion being defined by how the one switch is manipulated by the user; and performing sensitivity adjustment of the photoelectric sensor in order to set the reference received light amount to a value suitable for the setting of the threshold characterized in that the photoelectric sensor further comprises a display part that is configured to: indicate a character string that represents the number of times the one switch is being manipulated; indicate a character string that represents the one of the plurality indicate a character string that represents the number of times the one switch is being manipulated; indicate a character string that represents the one of the plurality of tunings determined by how the one switch is manipulated by the user; indicate by switching an indicating lamp from a lighting state to a blinking state when the one switch is continuously pressed for three seconds; and display the threshold, which is fixed based on the reference received light amount, together with the received light amount after sensitivity is adjusted indicate by switching an indicating lamp from a lighting state to a blinking state when the one switch is continuously pressed for three seconds; and display the threshold, which is fixed based on the reference received light amount, together with the received light amount after sensitivity is adjusted