A control circuit of a switching converter includes a current detection comparator for comparing a detection voltage corresponding to a voltage drop of a detection resistor with a reference voltage and generating a peak current detection signal asserted when the detection voltage reaches the reference voltage, a driving logic unit for generating a pulse signal indicating a turn-on/off operation of a switching transistor and changing the pulse signal to an OFF level indicating the turn-off operation of the switching transistor when the peak current detection signal is asserted, a driver for driving the switching transistor based on the pulse signal, and a reference voltage setting unit for measuring time (TRECT) for which a current flows through a secondary coil and a switching period (T) of the switching transistor and adjusting the reference voltage (VREF) according to an equation: VREF=K×T/TRECT where K is a coefficient.