An exhaust emission control device is used for an engine and is applied to an exhaust gas purifying system. The system has an NOx catalyst disposed in an exhaust passage of the engine to promote selective purification of NOx in exhaust gas performed by ammonia, which is a reducing agent for reducing NOx, and a reducing agent adding device for adding the reducing agent to an upstream side of the catalyst in a flow direction of exhaust gas. The device includes a catalyst temperature detecting device for detecting temperature of the catalyst, a reaction ratio calculating device for calculating a reaction ratio, which is a ratio of a reaction amount of ammonia to a reaction amount of NOx in the catalyst, based on the temperature of the catalyst, and an ammonia consumed amount calculating device for calculating a consumed amount of ammonia in the catalyst based on the reaction ratio.