Abstract: An engine knocking detecting device comprising an engine vibration sensor for sensing engine vibrations and producing electric signals representing the engine vibrations, a knocking detecting circuit including a knocking signal discriminating circuit such as a band pass filter for detecting signals representing engine vibrations caused by engine knocking and a knocking intensity detecting circuit for detecting durations of the signals representing the engine knocking vibrations to thereby detect intensity of the engine knocking. The knocking intensity detecting circuit may include a comparator for comparing the signal which have passed through the band pass filter with a reference value which may be varied in accordance with noise and producing an output when the signal from the filter means is greater than the reference value.