An ignition timing control system for an internal combustion engine, for controlling an ignition timing of the engine, is provided. A charging efficiency of the engine is calculated according to the intake air flow rate and the engine rotational speed which are detected, and a knock limit ignition timing is calculated according to the engine rotational speed and the charging efficiency. A knock correction value is calculated according to the knocking detection result by a knock sensor, and a learning parameter table, in which first and second learning parameters are set, is updated based on the engine rotational speed and the knock correction value when the knocking is detected. The learning parameter table is retrieved according to the engine rotational speed, to calculate the first and second learning parameters. Each-cylinder correction values are calculated corresponding respectively to a plurality of cylinders of the engine using the charging efficiency, the first learning parameter, and the second learning parameter and the ignition timing of the engine is controlled using the knock limit ignition timing and the each-cylinder correction value.