Current balance circuit of resonant type switching power-supply circuit

Provided is a switching power-supply device capable of balancing a plurality of converter blocks operated in parallel. The switching power-supply device includes a first series circuit of first and second switching elements, a second series circuit of third and fourth switching elements, which circuits are connected in parallel with a power supply, and a control circuit that turns on-and-off the first and second switching elements, alternately, with an arbitrary frequency and turns on-and-off the third and fourth switching elements, alternately, with the same frequency as the arbitrary frequency. The control circuit controls a phase difference of switching signals of the first and second series circuits.