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 (1b, 2b) and being configured to transmit either a signal which is input from the controller to the first or second control unit (1b, 2b) or a signal which is output from the first or second control unit (1b, 2b) to the controller, each of said signals being configured to contain a single different control or status; and a communicator (1e, 2e) connected to at least one of said plurality of signal wirings and configured to conduct communication between the first or second control unit (1b, 2b) 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 (1b, 2b) and being configured to transmit either a signal which is input from the controller to the first or second control unit (1b, 2b) or a signal which is output from the first or second control unit (1b, 2b) to the controller, each of said signals being configured to contain a single different control or status; and a communicator (1e, 2e) connected to at least one of said plurality of signal wirings and configured to conduct communication between the first or second control unit (1b, 2b) 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.