Disclosed is a proximity switch provided with an actuator unit and a sensor unit. The sensor unit is provided with an antenna coil, a transmitting circuit which transmits electromagnetic waves at a constant frequency to the antenna coil, a receiving circuit which detects external signals received by means of the antenna coil, and control circuits. The actuator unit is provided with an antenna coil, a power supply circuit which rectifies an electromotive force generated in the antenna coil, and a signal processing circuit which receives power supply from the power supply circuit, performs frequency-dividing to the signals received by means of the antenna coil, and transmits the signals from the antenna coil after the frequency-dividing. The control circuit of the sensor unit has memory for registering the frequency of the signals transmitted from the actuator unit. The control circuit determines whether the actuator unit is in proximity to the sensor unit or not by checking the received signals detected by means of the receiving circuit with the operations of the transmitting circuit and the frequency registered in the memory.