An object to be achieved by the present invention is to achieve ignition timing that is suitable for an environment in which a spark ignition internal combustion engine is used during the period of starting of the internal combustion engine and warm-up thereof just after starting. To achieve this object, according to the present invention, in an ignition control system for an internal combustion engine in which, ignition timing is controlled by feedback in such a way that the engine rotation speed becomes equal to a target rotation speed when the temperature of the internal combustion engine is lower than a prescribed temperature, and retard control for retarding the ignition timing by a predetermined amount from target ignition timing is performed when the temperature of the internal combustion engine is equal to or higher than the prescribed temperature, the aforementioned prescribed temperature is changed according to the altitude of the place where the internal combustion engine is used.