To perform accurate knocking determination without being influenced by temperature change.

Vibration signal (level) in a frequency band used for knocking determination obtained by frequency analysis of high frequency component of output of a knocking sensor is determined. Temperature correction coefficient corresponding to frequency band used for the knocking determination is selected from temperature correction coefficient characteristics established for each frequency band. A thermistor is connected to output terminal of the knocking sensor in parallel to detect temperature of the sensor from low frequency (direct current) component of out put of the knocking sensor. Temperature correction coefficient is determined from the temperature correction coefficient characteristics selected based on temperature of the sensor. Temperature correction is performed by multiplying the level of the vibration signal and the temperature correction coefficient together. Knocking determination is performed by comparing the vibration signal level subjected to temperature correction and a determination threshold.