Exhaust gas purification apparatus

A particulate filter (22) is arranged in an exhaust passage of an internal combustion engine. Whether the particulate deposited on the particulate filter (22) has changed in property to a property harder to oxidize compared with right after deposition is predicted or judged. When the fact that the particulate deposited on the particulate filter (22) has changed in property to a property harder to oxidize compared with right after deposition is predicted or judged, the air-fuel ratio of the exhaust gas flowing into the particulate filter (22) is switched temporarily from lean to rich.