A multi-optical axis photoelectric sensor comprising: a sensor unit configured to detect whether each of a plurality of optical axes formed between a projection unit and a light receiving unit is in a light shielding state, the sensor unit comprising the projection unit and the light receiving unit , the projection unit comprising a plurality of projection elements, the light receiving unit comprising a plurality of light receiving elements disposed opposite the plurality of projection elements; a first control unit configured to control the projection unit , the first control unit being provided in the projection unit ; a second control unit configured to control the light receiving unit , the second control unit being provided in the light receiving unit ; a controller connected to the first control unit and to the second control unit ; a plurality of signal wirings, each signal wiring connected to said controller and to said first or second control unit and being configured to transmit either a signal which is input from the controller to the first or second control unit or a signal which is output from the first or second control unit to the controller , each of said signals being configured to contain a single different control or status; and a communicator connected to at least one of said plurality of signal wirings and configured to conduct communication between the first or second control unit and an external device , characterized in that the sensor is adapted to use said at least one of the plurality of signal wirings as a common wiring through which to transmit the corresponding at least one of said signals to and from the controller and to conduct said communication with the external device . a sensor unit configured to detect whether each of a plurality of optical axes formed between a projection unit and a light receiving unit is in a light shielding state, the sensor unit comprising the projection unit and the light receiving unit , the projection unit comprising a plurality of projection elements, the light receiving unit comprising a plurality of light receiving elements disposed opposite the plurality of projection elements; a first control unit configured to control the projection unit , the first control unit being provided in the projection unit ; a second control unit configured to control the light receiving unit , the second control unit being provided in the light receiving unit ; a controller connected to the first control unit and to the second control unit ; a plurality of signal wirings, each signal wiring connected to said controller and to said first or second control unit and being configured to transmit either a signal which is input from the controller to the first or second control unit or a signal which is output from the first or second control unit to the controller , each of said signals being configured to contain a single different control or status; and a communicator connected to at least one of said plurality of signal wirings and configured to conduct communication between the first or second control unit and an external device , characterized in that the sensor is adapted to use said at least one of the plurality of signal wirings as a common wiring through which to transmit the corresponding at least one of said signals to and from the controller and to conduct said communication with the external device . <EOS>