This study was conducted to evaluate the safety of herbicide-resistant rice, a genetically modified organism (GMO) developed by the Rural Development Administration, in Sprague-Dawley rats. The nutrient content of herbicide-resistant polished and brown cooked rice was compared with that of conventional Ilpum polished and brown cooked rice to assess composition equivalence. Compositional analysis was performed to measure proximates, fiber, and minerals before animal feeding. Growing male rats were fed one of the following four diets for six weeks: Ilpum polished cooked rice (IP) and Ilpum brown cooked rice (IB) as a non-GMO and herbicide-resistant polished cooked rice (GP) and brown cooked rice (GB) as a GMO. We checked clinical symptoms (anorexia, salivation, diarrhea, polyuria, anuria, fecal change) every day, food intake, change of body weight twice a week, and serum biochemistry and organ weights after 6 weeks of experimental feeding among the four groups. Nutrient content of the herbicide-resistant rice was similar to that of the non-transgenic control and was within the published range observed for non-transgenic rice. We could not find any significant difference in the above-mentioned items as the index to be checked in the animals fed the GMO. These results suggest that the nutrient content of genetically modified herbicide-resistant rice is compositionally equivalent to that of conventional Ilpum rice and that growing male rats fed herbicide-resistant rice are no different from those fed Ilpum rice, non-GMO for 6 weeks.