To improve BER performance and to prevent the loss of carrier wave synchronization in environment where a receiving state rapidly and frequently changes by reducing the frequency of first automatic gain control causing the level fluctuation of an input signal to a demodulator.

At the same time of executing second automatic gain control processing to the output signal of a first AGC circuit, a first AGC circuit receives the input of a next received signal an executes first automatic gain control processing to this received signal (S16). Then the intensity of the output signal of the first AGC circuit is measured by a detection circuit (S17). After then, a microprocessor judges whether the measured value is within the second power control window W3 of an already decided band width larger than a first power control window W2 (S18). Then when the measured value is not within the second power control window W3, the microprocessor corrects the gain of the first AGC circuit (S19).