A multi-output switching power supply of the present invention includes: a series resonant circuit which is connected in parallel with a first switching element or a second switching element, and includes a current resonance capacitor, a resonant reactor and a primary winding of a transformer, which are connected in series; a first rectifying and smoothing circuit which rectifies and smoothes a voltage generated in a first secondary winding of the transformer, and outputs a first output; a second rectifying and smoothing circuit which has a first diode for rectifying a voltage generated in a second secondary winding of the transformer, a reactor having energy stored therein by the voltage rectified by the first diode and a second diode for regenerating the energy into an output, and which rectifies a current flowing through the reactor and outputs a second output; and a control circuit which alternately turns on and off the first and second switching elements based on the first output.