A novel amplitude deviation correction circuit which corrects an amplitude deviation between an I signal and a Q signal is disclosed. An average amplitude deviation between an I signal amplified by a variable gain amplifier and a Q signal amplified by another variable gain amplifier is detected by an amplitude comparison circuit, and +1 volt or -1 volt is outputted in response to a result of the detection. An integration circuit integrates the output of the amplitude comparison circuit and controls the gains of the variable gain amplifiers in response to a result of the integration.