To provide a switching control circuit that has excellent follow-up performance of an output current in a load variation and can improve voltage conversion efficiency, and also to provide a switching power supply using the switching control circuit.

The switching control circuit 15 is used by a forward type switching power supply for supplying power from a primary side of a voltage converter to a secondary one during the on period of a FET 16A, and controls the on/off operation of the FET 16A. The switching control circuit 15 is provided with: an average current control section 153 for deciding a period during which the FET 16A should be on so that an average current value of a primary current flowing from the primary side of the voltage converter to the FET 16A during the on period of the FET 16A nearly agrees with a preset target current value; and a time adjustment circuit 152 for adjusting the on and off periods of the FET 16A according to the on period during which the FET 16A decided by the average current control section 153.