An automatic gain control circuit having a variable gain amplifier circuit, a signal level detecting circuit connected to the variable gain amplifier circuit for generating a detect signal the level of which changes in response to a signal level of an output signal of the variable gain amplifier circuit, and a gain control circuit for controlling the gain of the variable gain amplifier circuit in accordance with the signal level of the detect signal, and the gain control circuit having a differential amplifier circuit having first and second input terminals, the first and second input terminals being connected to the signal level detecting circuit for receiving the detect signal, a first reference voltage source connected to the first input terminal of the differential amplifier so that a first predetermined voltage is provided instead of the signal level of the detect signal in response to the signal level of the detect signal and a second reference voltage source connected to the second input terminal of the differential amplifier for providing a second predetermined voltage.