PURPOSE: To suppress voltage fluctuation due to load fluctuation in a flyback type switching regulator circuit.

CONSTITUTION: A switching regulator circuit 1 is provided with a transformer 4, a semiconductor switching element 8 provided serially to a primary coil winding 4a1, a drive control circuit 9 for driving and controlling the semiconductor switching element 8, and a feedback part 10 for making constant the rectification output voltage of a secondary coil winding 4b1 by detecting the rectification output of the secondary coil winding 4b1 which is wound reversely with respect to the primary coil winding 4a1 out of the secondary coil windings of the transformer 4 and then transmitting it to the drive control circuit 9. A secondary coil winding 4b3 wound in-phase for the primary coil winding 4a1 of the transformer 4 is provided and rectification output is obtained without any feedback control for the secondary coil winding 4b3.