After the Fukushima Daiichi nuclear power plant accident triggered by the Great East Japan Earthquake on March 11, 2011, radioactive cesium (Cs) was released and widely distributed in agricultural field in Tohoku distinct. Radioactive Cs has relatively long half-lives, and thus contamination of agricultural products by radioactive Cs will be long-term serious problem for human health. Therefore, we have observed the levels of radioactive Cs contamination in rice plants grown in Fukushima from 2011 to 2014. Our study demonstrated that there is considerable variation in radioactive Cs concentration among a wide variety of rice cultivars grown in Fukushima paddy field. These results indicated that Cs accumulation levels were genetically regulated in rice plants. In addition, the high nitrogen and low potassium condition produced an increase in the Cs concentration both in straw and brown rice, suggesting that Cs accumulation levels in rice was also controlled by environmental factor.