Economic evaluation of a membrane-absorption hybrid system for separation of CO2 from a natural gas-fired power plant was performed. In this system, the feed gas (CO2/N-2 mixture) and carrier solution (aqueous mixed solution of diethanolamine and 2-(butylamino)ethanol) are both supplied to the lumen side (feed side, high pressure side) of the hollow fiber ultrafiltration membrane module and flow upward. The carrier or absorbent solution, which contains dissolved CO2, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to become a lean solution, and the lean solution is recycled to the lumen of the hollow fiber. In case 1, where the CO2 purity of the recovered gas is higher than 90% and the recovered gas is transported as a gas mixture for sequestration, the energy required for CO2 separation was estimated as 0.10 kWh/kg-CO2, and the CO, separation cost including energy cost and equipment cost was estimated as 3.09 yen/kg-CO2. In case 2, where the recovered CO2 is transported as liquefied gas, the required energy and separation cost were estimated as 0.22 kWh/kg-CO, and 5.14 yen/kg-CO2, respectively. These values were smaller than the corresponding values of conventional CO2 separation processes such as chemical absorption process and polymeric membrane separation process, which suggested that the present CO2 recovery system has an economic advantage over the conventional CO2 separation processes.