A control device for an internal combustion engine for controlling an internal combustion engine comprising: an engine body; a fuel feed system configured to directly feed fuel to a combustion chamber of the engine body; and an ozone feed system configured to directly or indirectly feed ozone to the combustion chamber, the control device comprises: a combustion control part configured to control the fuel feed system and the ozone feed system in a predetermined operating region so as to cause a difference in ozone concentration in the combustion chamber space-wise or time-wise so that the premixed gas burns inside the combustion chamber by compression ignition in stages; and an ozone malfunction judging part configured to judge malfunction of the ozone feed system in the predetermined operating region, the ozone malfunction judging part comprises: a self-ignition timing detecting part configured to detect a self-ignition timing of the premixed gas; a presumed self-ignition timing calculating part configured to calculate a presumed self-ignition timing of the premixed gas; a combustion noise detecting part configured to detect combustion noise when making a premixed gas burn by compression ignition; and a presumed combustion noise calculating part configured to calculate presumed combustion noise when making the premixed gas burn by compression ignition, and the ozone malfunction judging part is configured to judge that the ozone feed system is malfunctioning when the self-ignition timing is retarded from the presumed self-ignition timing and the combustion noise is larger than the presumed combustion noise or when the self-ignition timing is advanced from the presumed self-ignition timing and the combustion noise is smaller than the presumed combustion noise. an engine body; a fuel feed system configured to directly feed fuel to a combustion chamber of the engine body; and an ozone feed system configured to directly or indirectly feed ozone to the combustion chamber, the control device comprises: a combustion control part configured to control the fuel feed system and the ozone feed system in a predetermined operating region so as to cause a difference in ozone concentration in the combustion chamber space-wise or time-wise so that the premixed gas burns inside the combustion chamber by compression ignition in stages; and an ozone malfunction judging part configured to judge malfunction of the ozone feed system in the predetermined operating region, a combustion control part configured to control the fuel feed system and the ozone feed system in a predetermined operating region so as to cause a difference in ozone concentration in the combustion chamber space-wise or time-wise so that the premixed gas burns inside the combustion chamber by compression ignition in stages; and an ozone malfunction judging part configured to judge malfunction of the ozone feed system in the predetermined operating region, the ozone malfunction judging part comprises: a self-ignition timing detecting part configured to detect a self-ignition timing of the premixed gas; a presumed self-ignition timing calculating part configured to calculate a presumed self-ignition timing of the premixed gas; a combustion noise detecting part configured to detect combustion noise when making a premixed gas burn by compression ignition; and a presumed combustion noise calculating part configured to calculate presumed combustion noise when making the premixed gas burn by compression ignition, and a self-ignition timing detecting part configured to detect a self-ignition timing of the premixed gas; a presumed self-ignition timing calculating part configured to calculate a presumed self-ignition timing of the premixed gas; a combustion noise detecting part configured to detect combustion noise when making a premixed gas burn by compression ignition; and a presumed combustion noise calculating part configured to calculate presumed combustion noise when making the premixed gas burn by compression ignition, and the ozone malfunction judging part is configured to judge that the ozone feed system is malfunctioning when the self-ignition timing is retarded from the presumed self-ignition timing and the combustion noise is larger than the presumed combustion noise or when the self-ignition timing is advanced from the presumed self-ignition timing and the combustion noise is smaller than the presumed combustion noise.