An apparatus separating carbon dioxide from combustion gas using separation membranes, which includes: a first separation membrane in which combustion gas is injected into an inlet side of the first separation membrane; a second separation membrane in which residue gas of the first separation membrane is injected into an inlet side of the second separation membrane; and a third separation membrane in which permeate gas of the first separation membrane is injected into an inlet side of the third separation membrane, wherein at least a part of permeate gas of the third separation membrane is captured, and residue gas of the third separation membrane is injected into the inlet side of the first separation membrane or the second separation membrane. The present invention can be easily applied to an actual process by efficiently separating carbon dioxide using separation membranes.