Abstract: A control apparatus for an internal combustion engine is provided that can correct a shift in an output value of an in-cylinder pressure sensor that occurs for a predetermined time period after occurrence of abnormal combustion. A pre-occurrence output characteristic indicating a relationship between in-cylinder pressure and an actual sensor output value of the in-cylinder pressure sensor in a pre-occurrence cycle before occurrence of abnormal combustion is previously stored. Estimated in-cylinder pressure in a post-occurrence cycle after occurrence of abnormal combustion is acquired. A post-occurrence output characteristic is calculated from the estimated in-cylinder pressure and the sensor output value in the post-occurrence cycle. A difference between outputs of the in-cylinder pressure sensor before and after occurrence of the abnormal combustion is calculated from the pre-occurrence output characteristic and the post-occurrence output characteristic.