There is provided an exhaust gas treatment apparatus. The exhaust gas treatment apparatus includes: a main discharge passage through which exhaust gas of combustion equipment is discharged; an heat exchanger between the combustion equipment and the main discharge passage; a nitrogen oxide decreasing device connected to the main discharge passage to decrease nitrogen oxides of exhaust gas; a bypass connected from the combustion equipment to the main discharge passage as a passage bypassing the heat exchanger to supply high temperature exhaust gas from the combustion equipment to the nitrogen oxide decreasing device; and a variable exhaust regulator disposed between the bypass and the main discharge passage to vary the amount of relatively high temperature exhaust gas flowing in the bypass and the amount of exhaust gas flowing in the main discharge passage in a correlated manner.