Disclosed are an exhaust gas treating apparatus and a treating method for a carbon dioxide capture process, in which harmful substances remaining in the exhaust gas discharged from the conventional flue-gas desulfurization process are additionally removed for efficient performance of the carbon dioxide capture process. According to the exhaust gas treating apparatus for a carbon dioxide capture process, it has the effects of minimizing the installation space of desulfurization equipment and reducing the process cost. In addition, by keeping the contaminants contained in the gas introduced in the carbon dioxide capture equipment below a proper level, absorption performance can be improved as degradation of the absorbent used in the carbon dioxide capture process is prevented. After all, it has an advantage of preventing the pollution by the exhaust gas discharged into the atmosphere.