For wide-use of a power plant utilizing solar energy, the improvement of its economics is important. Both economics and characteristics of a CO₂-capturing solar thermal hybrid power generation system have been evaluated in this paper. Since relatively low temperature steam of 220°C is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine, the solar collector can attain high heat collecting efficiency. The net fuel-to-electricity conversion efficiency of the hybrid system was estimated to be higher than 60% on lower heating value basis. It has been estimated that the gross income and the period of depreciation of the proposed system are 34.8×10⁵ yen/year and 8.89 years, respectively, and that the system is economically feasible, when the system is assumed to have the solar collector area of 10 ha, the maximum net power output of 4 MW and the heat storage capacity of 2000m³. The amount of the fuel saving and the reduction of CO₂ emission of this system, compared to a conventional natural gas firing plant, have also been estimated in the paper.