Exhaust purification device of internal combustion engine

An exhaust purification device of an internal combustion engine in which an NO.sub.x absorber which absorbs NO.sub.x when the air-fuel ratio of an inflowing exhaust gas is lean and releases the absorbed NO.sub.x when the air-fuel ratio of the inflowing exhaust gas is the stoichiometric air-fuel ratio or rich is arranged in an engine exhaust passage, an air-fuel ratio sensor is arranged in the engine exhaust passage downstream of said NO.sub.x absorber, and NO.sub.x releasing completion decision means is provided for deciding that the releasing action of NO.sub.x from the NO.sub.x absorber is completed when the air-fuel ratio detected by the air-fuel ratio sensor is switched from lean to the stoichiometric air-fuel ratio or rich after the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber is switched from lean to the stoichiometric air-fuel ratio or rich and the releasing action of NO.sub.x from the NO.sub.x absorber is started.