Control device for internal combustion engine

A control device for an internal combustion engine can suppress electricity used for driving a microwave emitter and achieve reduction in exhaust emission. The internal combustion engine (100) is provided with an engine body (1), a catalyst device (34) provided in an exhaust passage of the engine body (1) and having an exhaust purification catalyst with at least an oxidation function and a microwave absorber contained in a catalyst coat layer (342) formed inside a substrate (341), and a microwave emitter (35) for irradiating the catalyst device (34) with microwaves. The control device (200) for the internal combustion engine is configured so that if engine startup is requested when a temperature of the exhaust purification catalyst is less than a predetermined temperature, it makes the microwave emitter (35) irradiate the catalyst device (34) with microwaves and operates the engine body so that an air-fuel ratio of exhaust discharged from the engine body (1) becomes a predetermined lean air-fuel ratio leaner