Abstract: Disclosed herein is a resonant converter, including: a power conversion circuit alternately switching applied DC power to output a predetermined level of output power; and a control circuit fixing an operating frequency and controlling the level of the output power by varying the comparison voltage level that is a comparison target of the operating frequency, by determining that a short circuit occurs when the output current of the power conversion circuit is a reference current or more by comparing the output current of the power conversion circuit with the reference current. By this configuration, the output current can be constantly controlled even when the short circuit occurs in the output of the resonant converter.