A sound output device of the present invention is one that receives a digital audio signal including a plurality of channels and performs digital signal processing on the received digital audio signal, and includes a detecting portion which detects peak values or effective values of the plurality of channels included in the digital audio signal. The sound output device also includes an electric power calculating portion which calculates necessary electric power to output sound of each of the channels according to the peak values or the effective values. The sound output device also includes a sound volume adjusting portion which adjusts sound volume of the digital audio signal according to a total of the necessary electric power calculated by the electric power calculating portion for each of the channels.