A signal transmission circuit, provided with: a transformer (11); a primary-side circuit (12) for generating, during a period of time in which an input signal varying at binary levels indicates a first level, a pulse signal for causing a unidirectional current to flow in the primary-side coil (L1) of the transformer, the pulse signal being generated at a period quicker than the variation period of the input signal, and generating, during a period of time in which the input signal indicates a second level, a pulse signal for causing a current of the opposite direction to the aforementioned direction to flow in the primary-side coil, the pulse signal being generated at a period quicker than the variation cycle of the input signal; and a secondary-side circuit (13) for distinguishing between the first and the second levels in accordance with voltages having different polarities generated in the secondary-side coil (L2) of the transformer, and thereby regenerating the input signal.
