PURPOSE: To receive always a signal with less error rate, by not applying the diversity system if the intensity of field is higher than a prescribed value but applying the diversity system to receive the signal if the intensity of field is lower than the prescribed value.

CONSTITUTION: A field intensity signal indicating an average field intensity for a short time is obtained by a field intensity detector 5 and is inputted to a comparator 9 and is compared with the output of the first reference voltage generator 10. If the input signal is lower than the reference signal, the output signal is led to an FF15 unless an oscillator 13 is stopped, and the FF output is inverted, and an antenna is switched. The output of the detector 5 is sent to a comparing circuit 16; and if the intensity of field is higher than a prescribed value continuously for a certain time, an integrating circuit 18 generates a control signal to stop the oscillating operation of the circuit 13. Thus, when the intensity of field is higher than the prescribed value, receiving of the diversity system is not performed.