To detect the inner pressure of a cylinder corresponding to the crank angle by correcting response delay in a processing system for a cylinder inner pressure detection signal.

A timer is started (S4) at the time when compression reaches the top dead point (S3) during the time when fuel is cut (S2). After that, when the cylinder inner pressure detection signal becomes the maximum, the timer is stopped and the duration measured by the timer is learned as the response delay in the processing system of the cylinder inner pressure detection signal. Then, in a case of sampling the detection value of the cylinder inner pressure, sampling is carried out with a delay by the response delay time from the crank angle timing.