The analog signal detecting circuit comprises a reference voltage generator that outputs a plurality of reference voltages, the number of the reference voltages being varied depending on a voltage width between a minimum voltage value and a maximum voltage value of an analog signal; a plurality of comparators that compares a voltage of the analog signal with each of the plurality of reference voltages output from the reference voltage generator; a plurality of pulse generators that outputs a plurality of pulse signals having widths among the plurality of pulse signals varied depending on a frequency of the analog signal; and a combiner circuit section that outputs the pulse signals from the plurality of pulse generators by summing up.