The characteristics of a CO2-capturing hybrid-type power generation system utilizing both the fossil fuel and solar thermal energy were investigated. In the system, relatively low temperature saturated steam is produced by using solar thermal energy and is utilized as the working fluid of a methane-firing gas turbine system. The proposed system is a hybrid-type system in which generated CO2 is recovered based on the method of oxygen combustion, and thus a high efficiency system without both emission of CO2 and thermal NOx. can be expected to be possible to construct even in the region where solar radiation conditions are not so good. The system with 1ha collector area was assumed to be constructed in Osaka city, and its characteristics have been investigated. It has been estimated through simulation study that the proposed system has high exergetic efficiency of 63.8% on the basis of the fuel exergy even when generated CO2 is captured, and that the net generated power is 1.75MW, capacity factor is 17.7%, and total exergetic efficiency is 19.6%, being 1.61, 1.70, and 1.61 times high, respectively, compared with that of a conventional solar thermal power generation system. It has also been shown that the system has relatively 32% higher exergetic efficiency compared with a future high-efficiency photovoltaic power generation system.