PURPOSE: To maximize the internal pressure of a cylinder and improve accordingly the combustion efficiency.

CONSTITUTION: The ignition advance angle is decided so as to obtain maximum cylinder internal pressure from the ignition advance angle correction amount determined through fuzzy presumption according to the previous presumed value of the ignition advance angle correction amount and the time-basis change amount of the internal pressure of a cylinder of engine and the ignition advance angle fundamental amount decided on the basis of at least one of the boost pressure and the engine revolving speed. Thereby the cylinder internal pressure can be maximized, and the combustion efficiency be improved accordingly.