A current resonance type DC-DC converter includes a transformer that has a primary winding and a secondary winding, a switching circuit that has a pair of first switching elements and that is connected to the primary winding, an AC/DC transfer circuit that has four rectifying devices, which are connected in full bridge and include a pair of second switching elements, that is connected to the secondary winding, that converts an AC voltage, which is induced at the secondary winding, into a DC voltage and that outputs the DC voltage, and a control circuit that controls ON and OFF operations of the pairs of the first and second switching elements. The control circuit controls the ON and OFF operations so as to synchronize the pair of the first switching elements with the pair of the second switching elements.