A couple of frequency doubler circuits 21 and 22 which multiplys a frequency of a reference oscillation signal outputted from a reference oscillator 12 is provided, thereby a frequency of a reference oscillation signal, as the greatest common divisor between a frequency (300 KHz) determined by multiplying the frequency (fx=75 KHz) of a crystal oscillator 11 by four and a frequency (54 KHz) determined by multiplying an assigned frequency per one channel in AM radio broadcasting by a prescribed divide ratio, can be higher than a conventional frequency. This way realizes the decrease of a divide ratio in a programmable counter 17, resulting in the reduction of the circuit scale, shortening of the lock-up time, and improvement of the S/N ratio.