A signal transmission circuit includes: a transformer; a primary side circuit that: generates a pulse signal, for flowing a current in a primary side coil of the transformer in one direction during a period in which an input signal changing at a binary level indicates a first level, in a cycle shorter than a change cycle of the input signal; and generates another pulse signal, for flowing a current in the primary side coil in another direction opposite to the one direction during a period in which the input signal indicates a second level, in another cycle shorter than the change cycle of the input signal; and a secondary side circuit that: distinguishes the first level and the second level according to a voltage having a different polarity which is generated in a secondary side coil of the transformer; and reproduces the input signal.
