An exhaust gas purifying apparatus for an internal combustion engine includes a lean control unit and a rich control unit. The lean control unit executes lean spike operation, in which an air-fuel ratio is temporarily changed in a lean direction by a lean change width relative to a reference air-fuel ratio. The rich control unit changes the air-fuel ratio in a rich direction by a rich change width relative to the reference air-fuel ratio after the lean control unit executes the lean spike operation such that the air-fuel ratio stays in a predetermined slightly rich region. The rich change width is smaller than the lean change width.