To provide a sound quality improving circuit and an audio amplifying circuit using the circuit, the former circuit improving sound clearness, and being easily made to be an IC, and especially, being suitable for driving a full-range speaker.

The circuit of the invention i ncludes a circuit in which at least 3 or more phase-shifting circuits are connected in tandem. Phase characteristics of the circuit gradually delay a phase of an audio input signal corresponding to a logarithmic increase of a frequency in an audio frequency range, and shift the phase in the range of 450 to 600 degree in total in the audio frequency range.