A method for recovering CO 2 from gasification gas containing CO, CO 2, COS and H 2 S, and for obtaining fuel gas to be supplied to a gas turbine for power generation, the method comprising: a step of dividing a flow of gasification gas into a first part and a second part; CO shift reaction steps of subjecting the first part of the gasification gas to conversion of CO in the part of the gasification gas into CO 2 with COS contained therein converting into CO 2 and H 2 S, the second part of the gasification gas not being subjected to the CO shift reaction steps, the CO shift reaction steps comprising a first CO shift reaction step and a second CO shift reaction step which are carried out in series; a first heat exchanging step for preheating the resulting part of the gasification gas after the first CO shift reaction step with the first part of the gasification gas to be supplied to the first CO shift reaction step; a COS conversion step of performing a second heat exchange between the second part of the gasification gas and the resulting part of the gasification gas after the second CO shift reaction step, so that a gas temperature of the second part of the gasification gas is set in the range 150°C-350°C to convert COS contained in said second part into H 2 S; a H 2 S absorption step of mixing the second resulting part of gasification gas after the COS conversion with the first resulting part of the gasification gas after the CO shift reaction, and absorbing and removing H 2 S from the thus obtained mixture gas; a CO 2 absorption step of absorbing, removing and recovering CO 2 from the resulting mixture gas from which H 2 S has been removed in the H 2 S absorption step; and a step of obtaining the resulting gas from which CO 2 has been removed in the CO 2 absorption step as the fuel gas for power generation. a step of dividing a flow of gasification gas into a first part and a second part; CO shift reaction steps of subjecting the first part of the gasification gas to conversion of CO in the part of the gasification gas into CO 2 with COS contained therein converting into CO 2 and H 2 S, the second part of the gasification gas not being subjected to the CO shift reaction steps, the CO shift reaction steps comprising a first CO shift reaction step and a second CO shift reaction step which are carried out in series; a first heat exchanging step for preheating the resulting part of the gasification gas after the first CO shift reaction step with the first part of the gasification gas to be supplied to the first CO shift reaction step; a COS conversion step of performing a second heat exchange between the second part of the gasification gas and the resulting part of the gasification gas after the second CO shift reaction step, so that a gas temperature of the second part of the gasification gas is set in the range 150°C-350°C to convert COS contained in said second part into H 2 S; a H 2 S absorption step of mixing the second resulting part of gasification gas after the COS conversion with the first resulting part of the gasification gas after the CO shift reaction, and absorbing and removing H 2 S from the thus obtained mixture gas; a CO 2 absorption step of absorbing, removing and recovering CO 2 from the resulting mixture gas from which H 2 S has been removed in the H 2 S absorption step; and a step of obtaining the resulting gas from which CO 2 has been removed in the CO 2 absorption step as the fuel gas for power generation.