A demodulation circuit of an optical disc apparatus performing an FSK demodulation by being provided with a binary signal which is obtained by binarizing a signal reproduced from an optical disc on which an FSK modulation signal is previously recorded, said demodulation circuit characterized by:

edge interval measuring means for measuring an edge interval of said binary signal;
subtracting means for obtaining an FSK modulation component from a difference between a measured edge interval value and a previously determined edge interval reference value;
first moving average means for obtaining a moving average of said FSK modulation component;
demodulation value calculating means for obtaining a demodulation value based on an average value output from said first moving average means;
second moving average means for obtaining a moving average of said demodulation value; and
comparing means for comparing an average value output from said second moving average means with a reference value so as to obtain a binary FSK demodulation signal.