An audio power amplifying apparatus includes first through B-th power amplifying terminals, each of which power-amplifies an input alternating current (AC) audio input signal input and outputs the power amplified result as an audio output signal. A preamplifier of a b-th amplifying terminal divides the audio input signal into positive and negative portions to preamplify the positive and negative portions. A power supply supplies first through M-th positive and negative voltages having different levels. A power amplifier selects a positive supply voltage having a level proportional to a level of the preamplified positive portion and a negative supply voltage having a level proportional to a level of the preamplified negative portion and again amplifies the preamplified positive and negative portions using the selected positive and negative supply voltages to be combined by a signal synthesizer as the audio output signal.