ENGINE EXHAUST GAS PURIFICATION APPARATUS

To effectively reduce the ammonia generation amount of a catalyst device in an engine exhaust gas purification apparatus, the apparatus includes a catalyst device that contains precious metals including palladium and rhodium and purifies exhaust gas, a linear air-fuel (A/F) sensor provided on an exhaust passage downstream of the catalyst device, and a control device that controls a fuel injection valve so as to set the air-fuel ratio of the exhaust gas to a target air-fuel ratio on the basis of the air-fuel ratio detected by the sensor. The control device determines whether the catalyst device is active and determines whether the catalyst device is deteriorated, and sets the target air-fuel ratio to a first air-fuel ratio to be leaner when determining that the catalyst device is not active and is deteriorated than when determining that the catalyst device is not deteriorated.