To utilize the area contaminated by radiation following the accident at Fukushima-Daiichi nuclear power plant, a case study was conducted of biomass gasification and gas engine system with the energy crop Erianthus grown in the area. The distribution of radioactive cesium in ash and gas components was estimated by the tube type lab-scale gasification test and the equilibrium calculation. As a result, the transfer ratio of cesium to the gas phase by gasification was lower than that by combustion because of less CsNO3 generation. Moreover, Erianthus grown in an area with less than approximately 9 million Bq/m(2) can be treated as normal biomass fuel. According to the feasibility study, biomass gasification system is economically feasible. According to the feasibility study, a biomass gasification system was shown to be an effective way of utilizing the radiation-contaminated area of Namie-machi, Fukushima where flat agricultural land exists.