An AM stereo receiver applicable to receive AM signals containing ID signals which represent different AM stereo systems. The AM stereo receiver includes an IF circuit for generating an IF signal based on a received signal, a PLL circuit for locking the frequency of the IF signal, a clock circuit for generating a clock signal based on a signal obtained from the PLL circuit, and ID signal detector for detecting any one of the ID signals and for producing a detected ID signal. A circuit for distinguishing which one of the different AM stereo systems does the detected ID signal represent includes a pulse generator for generating a first pulse signal having a pulse width as a function of the frequency of the detected ID signal, a counter for counting the number of the clock pulses occurring during said first pulse signal, and distinguish circuit for distinguishing each detected ID signal from different ID signals based on the counted result of the counter.