An internal combustion engine (1) causes an air/fuel mixture in a cylinder to combust due to ignition by a spark plug (14). The engine controller (50) calculates a crank angle at knock on the basis of an operating state of the engine (1) (53 54), calculates a knock intensity on the basis of this crank angle at knock (54), calculates a limit ignition timing at which knock is not generated, on the basis of the knock intensity (54), and controls the ignition timing of the spark plug (14) to the limit ignition timing at which knock is not generated (55). Therefore, suitable control of the ignition timing is achieved, by means of a small number of adaptation steps.