Abstract: A switching type power supply apparatus decreases the amount of power used in computer and computer peripheral devices by utilizing a switching transistor which is set into switching operation responsive to a pulse signal received from a power source control circuit. This switching transistor controls the voltage applied to the primary winding of the power transformer by the switching transistor, and issues an output voltage from the secondary winding. The power supply apparatus includes a switch circuit which is connected in series to the starting resistor for supplying the output voltage rectified from the AC power source when starting up to the power supply control circuit. The power supply apparatus includes a switch control circuit which turns off the switch circuit when the output voltage rectified from the AC output of the tertiary winding of the power transformer reaches a voltage high enough for stable operation of the power supply control circuit.