Provided is an exhaust gas purification device for an internal combustion engine, the exhaust gas purification device comprising: a NOx purification catalyst disposed within the exhaust gas conduit of the internal combustion engine and comprising base metal carried on a catalyst carrier; an oxygen sensor disposed at the position in the exhaust gas conduit which is downstream of the NOx purification catalyst; and an air-fuel ratio control means for controlling the air-fuel ratio of exhaust gas flowing into the NOx purification catalyst. When the NOx purification catalyst is subjected to predetermined oxygen poisoning, the air-fuel ratio control means controls the air-fuel ratio of the exhaust gas, which flows into the NOx purification catalyst, to a first air-fuel ratio which is richer than a theoretical air-fuel ratio and then, on the basis of an output value from the oxygen sensor, switches the air-fuel ratio of the exhaust gas, which flows into the NOx purification catalyst, to a second air-fuel ratio leaner than the first air-fuel ratio.