The economics of the civilian uses of nuclear energy, that is to say the economics of nuclear power generation in which its civilian uses has been virtually limited to power generation---has been the focus of much public discussion both internationally and domestically here in Japan. The reasons are that there are many underlying factors which determine the economics of power generation methods and that various assumptions can be made concerning these factors. In addition, the value of these factors will change over time and thus entail considerable uncertainties. Although there are many aspects to the economics of nuclear power generation, in its narrowest sense, it refers to the power generation costs of nuclear power plants and other arguments from other aspects can be summarized in terms of power generation costs. Therefore, this paper will focus on power generation costs at nuclear power plants. In this paper, I will introduce an outline of the economic evaluation of nuclear power generation by the Japanese Government, and describe its features by comparing this evaluation with an evaluation by the United States Government, and then point out what policy implications these economic evaluations have on nuclear power generation.