A 720-degree motor stage storage means for holding the result of stroke discrimination for the engine E also in the period for carrying out an idle stop control is provided. At the time of restarting the engine E from an idle stop state, a new stroke discriminating processing is not conducted, but the result of stroke discrimination stored in the 720-degree motor stage storage means is used, to thereby drive a fuel injection system and an ignition device. A stage decision unit for allocating a period of two revolutions of a crankshaft to 720-degree motor stages based on the result of stroke discrimination, a fuel injection and ignition stage correlation table having predetermined correlations of 720-degree motor stages with fuel injection stages and ignition stages, and restarting time motor stage conversion means for conversion of a 720-degree motor stage into a fuel injection stage and an ignition stage, are provided.