In a capacitor-discharge ignition system for an internal combustion engine having a power generation coil, a capacitor connected to the power generation coil, an ignition coil having a primary winding connected to the capacitor through a thyristor and a secondary winding connected to a spark plug, and a microprocessor which turns on the thyristor at a predetermined crank angular position to produce ignition in the spark plug, an engine stop switch is installed to input an engine-stop command signal to the microprocessor when being turned off by the operator. With this, it becomes possible to surely stop the engine at any time if desired.