Disclosed is a switching power source device for supplying a DC stabilized voltage to industrial or household electronic appliances. The power source device can restrict a change in the switching frequency due to the change in load so that low noise and high efficiency can be realized. The power source device includes a first rectifying and smoothing circuit and a second rectifying and smoothing circuit. The first rectifying and smoothing circuit includes a rectifying diode (7) and a smoothing capacitor (8). The second rectifying and smoothing circuit includes a rectifying diode (12) and a smoothing capacitor (13). In a closed circuit composed of the first rectifying and smoothing circuit and second rectifying and smoothing circuit which are connected by a transformer (3), leakage inductance between the primary winding (3a) and secondary winding (3c) of the transformer (3) is caused to resonate with the first or second rectifying and smoothing circuit so that a resonance current due to the resonance is taken as the current from the secondary winding (3c) to restrict occurrence of noise. <IMAGE>
