In the case when an exhaust gas amount is decreased, swirling power of an exhaust gas is maintained. To provide an exhaust gas treatment apparatus comprising: a reaction tower which has one or more openings through which an exhaust gas is introduced, and one or more exhaust gas introducing pipes which are provided corresponding to the one or more openings and carry the exhaust gas, wherein in the one or more openings, an opening area which contributes to introducing the exhaust gas into the reaction tower is variable. The reaction tower has two or more openings with different areas, and the respective exhaust gas introducing pipes corresponding to two or more openings with different areas has a selecting unit which selects whether to introduce the exhaust gas into the reaction tower or not.