Abstract: An ignition timing control device for a turbo-charged internal combustion engine which retards or advances the ignition timing in accordance with the load condition on the engine. The control device acts on a timing adjustment mechanism attached to the distributor to control the ignition timing as a function of the intake manifold pressure. The control device has a housing and a yieldable wall, such as a diaphragm, in the housing forming a pressure chamber on one side thereof. A pressure line is connected to the pressure chamber and opens into the intake manifold at a point swept by the throttle. The manifold pressure, which at that point varies with changes in engine load, is transmitted through the line to the pressure chamber to act on the diaphragm. The diaphragm is coupled to the ignition timing adjustment mechanism so that the timing is advanced or retarded in response to the displacement of the diaphragm.