An exhaust smoke processing system capable of economically removing heavy metal, comprising a air preheater 3 for heating combustion air by exhaust smoke discharged from a boiler 1, a heat recoverer 11 for heating a heat medium by exhaust smoke discharged from the air preheater 3, a dust collector 4 for collecting soot and dust in exhaust smoke discharged from the heat recoverer 11, a wet-type exhaust smoke processing apparatus for processing exhaust smoke discharged from the dust collector 4, a reheater 13 for heating exhaust smoke discharged from the wet-type exhaust smoke processing apparatus by the heat medium, and a heat medium circulation pipe passage 15 for circulating the heating medium between the reheater 13 and the heat recoverer 11, wherein the heating medium circulation pipe 15 is provided with temperature control means which measures a heavy metal concentration in exhaust smoke discharged from any one or more of the dust collector 4, the wet-type exhaust smoke processing apparatus 6 and the reheater 13, and adjust the temperature of exhaust smoke at an outlet of the heat recoverer 11 such that the measured value falls within a predetermined range.