To provide a DC power supply circuit which can sharply reduce losses in a no-load condition during the waiting operation.

In a DC power supply circuit for obtaining a DC current from the secondary side via a rectifying circuit by providing a transformer 1 and then connecting a commercial power supply 2 to a primary side, switching circuits 5, 6 for turning on and off the commercial power supply are provided between the primary side of the transformer 1 and the commercial power supply 2, the rectifying circuit is provided with a circuit 22 for detecting that a DC output voltage is larger or smaller compared to a constant value and a drive circuit 7 for turning on and off the switching circuit 5, 6 based on the detection result, in order to turn on and off the switching circuits 5, 6 depending on the load of the DC power supply circuit.