The present invention prevents sound quality from degrading due to a change in electric field intensity or due to multi-path noise. An arithmetic unit subtracts a signal based on the detection signal of multi-path noise whose time constant is specified by a second time constant circuit from a signal based on an RSSI signal whose time constant is specified by a first time constant. An output signal from this arithmetic unit is applied, as a control signal, to a stereo-noise control circuit or the like. This can control the degradation of separation and the like in accordance with multi-path fading to prevent sound quality from degrading.