The foot switch includes a pedal, an output command signal generating section generating, when the pedal is operated, an output command signal commanding an apparatus main body having a function of producing active output to produce active output, a communication section performing communication with the apparatus main body, a transmit power adjusting section adjusting transmit power of the output command signal in the communication section, and a storage battery supplying electric power to the output command signal generating section, the communication section and the transmit power adjusting section. The transmit power adjusting section adjusts the transmit power on the basis of a signal indicative of receiving-condition of the output command signal in the apparatus main body, the signal transmitted from the apparatus main body and received by the communication section.