Abstract: Signal transmitting device, signal receiving device, signal transceiver device and signal transmission method use a conductive case as a transmission line to transmit/receive a modulated control signal or a sensing signal. The signal transmitting device, the signal receiving device and the signal transceiver device adopt a capacitive coupling unit as a media to transmit/receive the modulated signal, which makes the conductive case as a carrier when coupling the modulated signal onto the conductive case. When the signal is carried on the conductive case, the modulated signal is able to be captured and well transmitted.