An in-cylinder pressure detecting apparatus for an internal combustion engine, for detecting an in-cylinder pressure which is a pressure in a combustion chamber of the engine. The in-cylinder pressure is detected by an in-cylinder pressure detecting block, and a motoring pressure corresponding to an in-cylinder pressure when no combustion is performed in the combustion chamber, is estimated. A peak value of the detected in-cylinder pressure is obtained as a detected pressure peak value in a predetermined operating condition of the engine. An estimated motoring pressure peak value which is a peak value of the estimated motoring pressure and corresponds to the detected pressure peak value, is calculated. The detected pressure peak value is compared with the estimated motoring pressure peak value, and sensitivity correction of the in-cylinder pressure detecting block is performed based on a result of the comparison. The predetermined operating condition is an operating condition in which an exhaust gas temperature raising control is performed for raising a temperature of exhaust gases from the engine by increasing an intake air amount of the engine and retarding an ignition timing of the engine.