To provide a bidirectional resonant converter that improves power efficiency over a wide load range and outputs the same voltage and power in both directions.

A first circuit 11 and a second circuit 12 can be connected via a transformer 13 to implement bidirectional power supply between the first circuit 11 and the second circuit 12. For power supply from the second circuit 12 to the first circuit 11, switching means 30 is switched such that resonance capacitors 26 of the second circuit do not contribute to a resonance action, and the first circuit 11 functions as a voltage doubler rectifier circuit. For power supply from the first circuit 11 to the second circuit 12, the switching means 30 is switched such that the resonance capacitors 26 of the second circuit contribute to a resonance action, and the second circuit 12 functions as a voltage doubler rectifier circuit if a load voltage is high and functions as a full wave rectifier circuit if the load voltage is low.