To provide an exhaust emission control device of an internal combustion engine can accurately estimate a deterioration degree of a catalyst.

The exhaust emission control device of an engine 1 is provided with a catalyst converter 16 (catalyst C) provided in an exhaust passage 13 and purifying the exhaust. The exhaust emission control device is further provided with an exhaust temperature sensor 21 for detecting a temperature (exhaust temperature TE) of the exhaust flowing to the catalyst C, and a bed temperature sensor 22 for detecting a temperature (catalyst bed temperature TC) of an end of the exhaust upstream side of the catalyst C. An electronic control device 2 calculates a rise degree T (=TC-TE) of the catalyst bed temperature TC with respect to the exhaust temperature TE flowing into the catalyst C based on the exhaust temperature TE and the catalyst bed temperature TC when the temperature of the exhaust flowing to the catalyst C through execution of PM regeneration is raised, and estimates the deterioration degree of the catalyst C based on the exhaust temperature TE when the rise degree T is equal to or more than a prescribed degree Tact.