A knocking detecting apparatus for an internal combustion engine, which can more accurately perform the knocking determination based on frequency components of the output signal of the knock sensor, is provided. A frequency spectrum analysis of the knock sensor output signal is performed at predetermined angular intervals of the crankshaft rotation angle. Intensities of a plurality of frequency components obtained by the frequency spectrum analysis are stored as time series data. The time series data of the frequency component intensity are binarized, and it is determined whether or not a knocking has occurred based on the binarized time series data.