Disclosed herein is an automatic gain control circuit including a power detector. The automatic gain control circuit includes a receiving unit for receiving an RF signal and a gain control unit for controlling the gain of the receiving unit. The receiving unit comprises an amplification part including a low noise amplifier and a gain amplifier for amplifying the RF signal, a mixer for down-converting and tuning the RF signal output from the gain amplifier, a low pass filter for receiving the down-converted signal from the mixer, and an intermediate frequency variable gain amplifier for amplifying the signal filtered by the low pass filter to an intermediate frequency signal. The gain control unit comprises a received signal strength indicator connected to the output port of the low pass filter to detect the level of the output signal of the low pass filter, a first comparator for comparing the output signal level detected by the received signal strength indicator with a reference signal level, a power detector for detecting the output signal level of the amplification part of the receiving unit, a second comparator for comparing the output signal level detected by the power detector with a reference signal level, and a gain controller for increasing, decreasing or holding the gain in response to the signals output from the first and second comparators.