An equalizer includes: a first attenuating circuit which receives an input signal and a first control signal and attenuates the input signal depending on the level of the first control signal; a filter having a predetermined frequency band which receives the output from the first attenuating circuit; an adding circuit which receives the output from the filter and the input signal so as to add the both and outputs the adjusted audio signal; a second attenuating circuit which receives the adjusted audio signal from the adding circuit and a second control signal, attenuates the adjusted audio signal depending on the level of the second control signal and sends out a phase inverted signal of the attenuated signal to the filter; wherein when a sound quality adjusting signal representing a sound quality emphasis is received, the first control signal having a level corresponding to the emphasis condition is generated and when a sound quality adjusting signal representing a sound quality attenuation is received, the second control signal having a level corresponding to the attenuation condition is generated.