To provide an integrated gasification fuel cell power generation system generating electricity by utilizing carbon dioxide obtained secondarily in wet fine desulfurization for a fuel cell.

This integrated gasification fuel cell power generation system where a fused carbonate fuel cell is incorporated into an integrated gasification combined cycle is operated as follows: (1) sulfur content in gasified gas generated is desulfurized in a wet fine desulfurizer 13; (2) carbon dioxide absorbed in a desulfurizing fluid of the desulfurizer is separated to be fed to the cathode 21 of a fuel cell 20, and part of gasified gas after desulfurized is fed to the anode 22; (3) exhaust gas discharged from the anode is returned to the desulfurizer through a water scrubber such as a wet deduster 11.