A switching power supply apparatus has a power circuit unit, the power circuit unit including a first switching element connected at a first end to a first end of a power supply, an inductor connected at a first end thereof to a second end of the first switching element, a second output terminal connected to a second end of the inductor, a capacitor connected between a first output terminal and the second output terminal, and a second switching element connected between a second end of the power supply and a second end of the first switching element. The switching power supply apparatus has an optimal response multi-mode digital current program mode control unit, the optimal response multi-mode digital current program mode control unit including an error signal generator which generates an error signal according to a potential difference between an output voltage and a preset voltage, and an inductor current detector which detects and amplifies an inductor current.