A signal transmission circuit with a first circuit in a signal transmission side having first and second semiconductor switch elements transmitting a reference potential or power supply voltage of the first circuit to a second circuit by being alternatively driven on and off according to a multiple of signals. The second circuit in a signal reception side having a voltage conversion circuit, including an in-phase noise filter that eliminates in-phase noise superimposed on the voltage transmitted via the first and second semiconductor switch elements, generating first and second pulse signals in accordance with the transmitted voltage, a latch circuit latching each of the first and second pulse signals with the first and second pulse signals as a clock, and a signal analysis circuit analyzing the first and second pulse signals latched by the latch circuit, and generating an output signal according to the category of the multiple of signals.