PURPOSE: To improve the durability, fuel consumption and output property of an engine by providing an ignition timing offsetting means for changing the offset ignition timing of cylinders on the basis of knocking condition and changing condition of knocking judgement.

CONSTITUTION: A cylinder in which the knocking condition is calculated to be lower than a predetermined one by a knocking condition calculating means MC and further the knocking judgement is considered lower than a predetermined one by a knocking judging means MD is first offset advanced a predetermined value by an ignition timing offsetting means MF. On the basis of the knocking condition and changing condition of knocking judgement due to the offset advance is altered the offset advance amount of said cylinder, while the ignition timing of cylinder provided with a knocking sensor MB is controlled by an ignition timing controlling means ME. Thus, the cylinder in which S/N ratio is degraded becomes difficult to generate knocking compared with other cylinders so that the durability, fuel consumption and output property of an engine are improved.