Abstract: In start of an engine, an ignition signal having a constant advance angle with respect to a top dead center of the engine is generated, and in idling state after a predetermined time period of start of the engine, the ignition signal is intercepted by a first masking circuit, and then number of pulses which are issued for predetermined revolution angles of the engine is counted; and ignition signals which are retarded from the above-mentioned ignition signal are output for a predetermined numbers of the pulses; furthermore in a predetermined range of opening degrees of the throttle valve, the ignition timing of the ignition signal is advanced responding to the opening degree of the throttle valve, and in a range over the predetermined opening degree of the throttle valve, the advance angle of the ignition timing is held at a constant value.