A circulating-current reducing circuit is provided that can suppress a circulating current with a simplified configuration having no control circuit. The circulating-current reducing circuit is connected to a transformer unit to reduce circulating current. The transformer unit includes: a first transformer device; a second transformer device that is connected to the first transformer device in parallel; and a switching element that controls timing of supply of current to a primary coil portion of the first transformer device and a primary coil portion of the second transformer device. The circulating-current reducing circuit includes a first circuit that is connected between the primary coil portion of the first transformer device and the switching element, and a second circuit that is connected between the primary coil portion of the second transformer device and the switching element.