PURPOSE: To provide an ignition timing controller which is improved so that the stable knock control is carried out in all the cylinders when one detector is broken, in an internal combustion engine equipped with a plurality of knock detecting means.

CONSTITUTION: The first and second knock detectors 111 and 112 are set for a multicylinder type internal combustion engine. Each detection signal supplied from the knock detectors 111 and 112 is supplied into a control circuit 14, and the ignition timing of each cylinder is controlled on the basis of the detected state of the knock. The control circuit 14 monitors the generation of troubles on the basis of the signal supplied from each detector 11, 12 and if the knock detector in trouble is detected, the cylinder group corresponding to the detector is angle-delayed to the degree where the generation of knocking is suppressed, and the cylinder group corresponding to the detector in normal state is angle- advanced to the state where knock is easily generated. Then, knock control is executed on the basis of the detection signal supplied from the knock detector in normal state.