To make one CPU perform the A/D conversion of another signal required by engine control other than knocking detection by setting the specified period of a sampling means picking up a knocking signal, to be the length of time capable of performing an A/D conversion more than two integral times in an A/D conversion means.

The engine control device including knocking detection, is made up of an A/D converter 40b provided with converting performance for general required convertion time as a sampling means connected to a knocking sensor 4, an A/D converter 40a as a different smapling means, a frequency analyzing part 47c provided with analyzing performance for specified frequencies, a BGL part and a knocking judging part 49 as a knocking judging means, and of one CPU 2 including an ignition operating part as an ignition operating means. By this constitution, the A/D conversion of a signal from an air flow sensor 5 can be performed within the period of smapling for the knocking signal of the knock sensor 4 without a hitch for a detection of knocking.