CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE AND CATALYST ABNORMALITY DIAGNOSIS METHOD

A control device for an internal combustion engine includes an electronic control unit that controls the air-fuel ratio of incoming exhaust gas flowing into a catalyst. The electronic control unit performs oxygen amount variation control in which a target air-fuel ratio for the incoming exhaust gas is switched between a rich set air-fuel ratio and a lean set air-fuel ratio. The electronic control unit switches the target air-fuel ratio to the rich set air-fuel ratio when an air-fuel ratio detected by an air-fuel ratio sensor is equal to or higher than a predetermined oxygen saturation determination air-fuel ratio. The oxygen saturation determination air-fuel ratio is leaner than an oxygen depletion determination air-fuel ratio and richer than the stoichiometric air-fuel ratio.