A signal transmitting apparatus using a plane coil for a sending coil and a receiving coil respectively, so that the outer diameters of the sending coil and the receiving coil can be decreased, and a signal can be stably transmitted from a sending side to a receiving side. The signal transmitting apparatus is provided with: a sending coil driven by an inputted signal; a receiving coil configured to output a received signal in response to the sending coil being driven; a pre-processing circuit to which the received signal outputted by the receiving coil is inputted; and a detecting circuit configured to detect the inputted signal from a signal outputted by the pre-processing circuit.