An exhaust gas treatment device comprising: a first exhaust gas flow path (L 11-1 ) where a first combustion exhaust gas (G 11-1 ) discharged from a first power generation facility (10-1) flows through; a second exhaust gas flow path (L 11-2 ) where a second combustion exhaust gas (G 11-2 ) discharged from a second power generation facility (10-2) flows through; an exhaust gas exhaust flow path (L 12-1 ) (L 12-2 ) disposed by branching off from each of the first exhaust gas flow path (L 11-1 ) and the second exhaust gas flow path (L 11-2 ), and configured to discharge an exhaust combustion exhaust gas to outside, the exhaust combustion exhaust gas including at least a part of each of the first combustion exhaust gas (G 11-1 ) flowing through the first exhaust gas flow path (L 11-1 ) and the second combustion exhaust gas (G 11-2 ) flowing through the second exhaust gas flow path (L 11-2 ); a nitrogen oxide removing unit configured to remove nitrogen oxide contained in an integrated combustion exhaust gas obtained by integrating the first combustion exhaust gas (G 11-1 ) from the first exhaust gas flow path (L 11-1 ) with the second combustion exhaust gas (G 11-2 ) from the second exhaust gas flow path (L 11-2 ); an integrated waste heat recovery unit configured to recover waste heat from the integrated combustion exhaust gas with nitrogen oxide removed by the nitrogen oxide removing unit; and a CO 2 recovery unit configured to recover CO 2 contained in the integrated combustion exhaust gas by using CO 2 absorbing liquid, the exhaust gas exhaust flow paths (L 12-1 ) (L 12-2 ) being branched off between the first power generation facility (10-1) or the second power generation facility (10-2) and the nitrogen oxide removing unit ; the exhaust gas treatment device further comprising a control unit configured to control a flow rate of the first combustion exhaust gas (G 11-1 ) and the second combustion exhaust gas (G 11-2 ) both introduced to the integrated waste heat recovery unit . a first exhaust gas flow path (L 11-1 ) where a first combustion exhaust gas (G 11-1 ) discharged from a first power generation facility (10-1) flows through; a second exhaust gas flow path (L 11-2 ) where a second combustion exhaust gas (G 11-2 ) discharged from a second power generation facility (10-2) flows through; an exhaust gas exhaust flow path (L 12-1 ) (L 12-2 ) disposed by branching off from each of the first exhaust gas flow path (L 11-1 ) and the second exhaust gas flow path (L 11-2 ), and configured to discharge an exhaust combustion exhaust gas to outside, the exhaust combustion exhaust gas including at least a part of each of the first combustion exhaust gas (G 11-1 ) flowing through the first exhaust gas flow path (L 11-1 ) and the second combustion exhaust gas (G 11-2 ) flowing through the second exhaust gas flow path (L 11-2 ); a nitrogen oxide removing unit configured to remove nitrogen oxide contained in an integrated combustion exhaust gas obtained by integrating the first combustion exhaust gas (G 11-1 ) from the first exhaust gas flow path (L 11-1 ) with the second combustion exhaust gas (G 11-2 ) from the second exhaust gas flow path (L 11-2 ); an integrated waste heat recovery unit configured to recover waste heat from the integrated combustion exhaust gas with nitrogen oxide removed by the nitrogen oxide removing unit; and a CO 2 recovery unit configured to recover CO 2 contained in the integrated combustion exhaust gas by using CO 2 absorbing liquid, the exhaust gas exhaust flow paths (L 12-1 ) (L 12-2 ) being branched off between the first power generation facility (10-1) or the second power generation facility (10-2) and the nitrogen oxide removing unit ; the exhaust gas treatment device further comprising a control unit configured to control a flow rate of the first combustion exhaust gas (G 11-1 ) and the second combustion exhaust gas (G 11-2 ) both introduced to the integrated waste heat recovery unit . <EOS>