An audio signal amplifier circuit and an audio device are characterized by comprising: an arithmetic circuit which receives digital audio signals and generates in response to digital control signals for sound volume adjustment, calculated digital values corresponding to the sound volume adjustment; a D/A converter circuit which D/A converts the calculated digital values from the arithmetic circuit and generates analogue values; a pulse generating circuit which generates pulses having a predetermined frequency of which generation period is PWM-modulated in response to output analogue values of the D/A converter circuit; and a driving current generating circuit which receives the pulses of the pulse generating circuit and generates current values corresponding to the PWM modulation, and wherein a speaker is driven in response to outputs from the current value generating circuit.