An exhaust gas purifying apparatus for an internal combustion engine, comprising: a catalyst that is placed in an exhaust passage of the internal combustion engine; outlet gas temperature measuring means for measuring an outlet gas temperature of the exhaust gas at a catalyst outlet; inlet gas temperature obtaining means for obtaining an inlet gas temperature of an exhaust gas at a catalyst inlet; catalyst temperature estimating means for estimating a catalyst temperature of the catalyst at each region of the catalyst divided into a plurality of parts; outlet gas temperature estimating means for estimating the outlet gas temperature considering degree of influence of the inlet gas temperature and a rear end temperature of the catalyst, wherein the degree of influence is high when the influence of the inlet gas temperature is larger than the influence of the rear end temperature; and temperature correcting means for correcting an estimated value of the catalyst temperature estimated by the catalyst temperature estimating means at each region of the catalyst, wherein the temperature correcting means calculates an estimated value correction amount based on a deviation between the estimated value of the outlet gas temperature estimated by the outlet gas temperature estimating means and a measured value of the outlet gas temperature measured by the outlet gas temperature measuring means, and uses the estimated value correction amount to correct the estimated value of the catalyst temperature at each region of the catalyst, and wherein the temperature correcting means corrects the estimated value correction amount at a region closer to the catalyst inlet largely and corrects the estimated value correction amount at a region closer to the catalyst outlet small, as the degree of influence becomes high. a catalyst that is placed in an exhaust passage of the internal combustion engine; outlet gas temperature measuring means for measuring an outlet gas temperature of the exhaust gas at a catalyst outlet; inlet gas temperature obtaining means for obtaining an inlet gas temperature of an exhaust gas at a catalyst inlet; catalyst temperature estimating means for estimating a catalyst temperature of the catalyst at each region of the catalyst divided into a plurality of parts; outlet gas temperature estimating means for estimating the outlet gas temperature considering degree of influence of the inlet gas temperature and a rear end temperature of the catalyst, wherein the degree of influence is high when the influence of the inlet gas temperature is larger than the influence of the rear end temperature; and temperature correcting means for correcting an estimated value of the catalyst temperature estimated by the catalyst temperature estimating means at each region of the catalyst, wherein the temperature correcting means calculates an estimated value correction amount based on a deviation between the estimated value of the outlet gas temperature estimated by the outlet gas temperature estimating means and a measured value of the outlet gas temperature measured by the outlet gas temperature measuring means, and uses the estimated value correction amount to correct the estimated value of the catalyst temperature at each region of the catalyst, and wherein the temperature correcting means corrects the estimated value correction amount at a region closer to the catalyst inlet largely and corrects the estimated value correction amount at a region closer to the catalyst outlet small, as the degree of influence becomes high.