An exhaust emission control system of an internal combustion engine calculates the PM deposition amounts of local regions in the filter, by a simple method. When a prescribed temperature raising process is performed in the filter including a first region and a second region along an exhaust stream, the calculated deposition amount of the first region is larger as a proportion of a magnitude of a first differential pressure reduction amount, as an exhaust differential pressure sensor detecting value in a first oxidation period, to the length of the first oxidation period is larger, and the first oxidation period is at least a part of a period from a point in time at which a temperature of the first region exceeds a predetermined oxidation start temperature, to a point in time at which a temperature of the second region exceeds the predetermined oxidation start temperature. The calculated deposition amount of the second region is larger as a proportion of a magnitude of a second region partial reduction amount corresponding to a differential pressure reduction amount for the second region, out of the second differential pressure reduction amount as an exhaust differential pressure sensor detecting value in a second oxidation period, to the length of the second oxidation period is larger, and the second oxidation period is a period from a point in time at which the temperature of the second region exceeds the predetermined oxidation start temperature during execution of the prescribed temperature raising process.