An AGC circuit includes: a variable gain amplifier circuit having a gain controlled with a gain control signal; a rectifier circuit for rectifying an output signal of the variable gain amplifier circuit; a voltage comparator for comparing a rectified signal with a threshold voltage; an up/down counter that switches between up-counting and down-counting according to the level of an output voltage of the voltage comparator; and a D/A converter circuit for outputting a voltage corresponding to a count value of the up/down counter. The gain control signal supplied to the variable gain amplifier circuit corresponds to the voltage output from the D/A converter circuit, and the threshold voltage for the voltage comparator is a voltage corresponding to the voltage output from the D/A converter circuit.