The authors intend to develop the environmental education in using the urban heat island as one of very poular phenomena observed in most of the cities in Japan and the world. In this study, they consider that the purpose of the enviroumental education is to bring up ervironmental ethics according to the understanding of physical system. The meaning of bringing up the environmental ethics is recognized as educating the way of thinking for the better environmental creation from the viewpoint of environmental conservation. Learning by the experience is one of the best ways in of education to understand physical environmental system. For this purpose, the urban heat island phenomena can be considered to be a very good example because about three quaters of Japanese people are living in the urbanized area.<br>The understanding of physical system means the understanding of earth's radiative equilibrium because solar energy is the only one energy that the earth receive within the solar system. In other words, it is to recognize the radiation balance and heat balance (the concept of net radiation) of the earth-atomspheric system. Therefore, in this study, more global physical system, the solar-earh system, is applied for the fundamental system instead of the ecosystem which has been accepted for Japanese environmental problems.<br>In recent years, the most serious problem for human physical environment, in other words, the disruption of the system, is the thermal pollution because most of the energy used by human activities are released for the space ultimately as the heat. Those activities occur within the urbanized area intensively and develop the urban heat island phenomena as one of the typical thermal pollution.<br>People intend to keep their active physical environment from the thermal pollution because its system is suitable for them. This means that they intend to continue earth's active radiation equilibrium. Therefore, the authors concluded that the urban heat island phenomena was the one of the best teaching subjects for the environmental education both for the the understanding of the system and for the learning by experience.