A knock control apparatus for internal combustion engines includes a plurality of sensors for generating signals indicative of the operating conditions of an engine, a plurality of actuators responsive to control signals to control the respective energy conversion functions of the engine, a data processing unit responsive to the signals from the sensors to perform engine controlling data processing operations and thereby supply engine control values to the actuators, and a knock sensing unit for detecting the occurrence of knocking in the engine and generating knock detection signals, and the data processing unit is responsive to the knock detection signals from the knock sensing unit to retard the calculated ignition timing. When the acceleration of the engine is detected in accordance with the output signal of the sensor, the data processing unit increases, in accordance with the knock detection signals, an amount of ignition timing retard to be calculated over an amount of retard to be calculated in accordance with the knock detection signals during the steady operation of the engine.