Chiyoda-city, the political and economic center of Japan, is consuming a great deal of energy, with its highly integrated business functions. Therefore, the city enacted “Global Warming Act, ahead of other cities, which declares the middle-term target ”to reduce 25% CO2 emission by 2020 below 1990 level.” The city will establish the society in which the environment and economy go together, through the activities including “Green Stock Strategy,” which is the energy conservation program of small to middle buildings and the “Chiyoda Eco System,” which is the environment management system unique to the city.