PURPOSE: To dispense with the treatment labor for the solid such as Cd or Cr separated from the liquid discharged after gypsum is removed in a flue gas desulfurizer.

CONSTITUTION: In an exhaust gas treatment apparatus wherein the exhaust gas discharged from combustion machinery is guided to a flue gas desulfurizer 9 and brought into contact with an absorbing soln. containing a calcium type absorbent to be subjected to desulfurization treatment and formed gypsum is removed from the absorbing soln. after desulfurization treatment and a part of the absorbing soln. is discharged, an impurity separator 22 precipitating impurities such as Cd and Cr dissolved in the soln. to separate the same is provided to a soln. drain line 21. The solid supply device 36 supplying the solid separated by the impurity separator 22 to the combustion machinery 1 is provided to incinerate the solid by the combustion machinery 1.