"Eco museum and sustainability: The term "eco museum" refers to ecological activities that aim to develop an entire region as a living museum. The word eco museum comes from the French word écomusée, a compound of ecology and museum. The word "eco" used as the root of ecology or economy is from the Greek word "oikos," meaning "house." It is not only a "museum of ecology" but a "area as a museum" This study is to make it clear how the eco museum concept becomes important methodology for making a sustainable society. Elements of eco museum: An eco museum embodies three elements: (1) the preservation of various kinds of heritage, including nature and cultural and industrial traditions, in a given region, (2) the management and operation of these with the participation of local residents for the sake of their own futures, and (3) the function of the preserved nature and traditions as a museum. Ideally, as shown in the diagram, the three elements of "heritage," "participation" and "museum" should be well balanced and constitute a closely integrated whole. In Japan today, there are only a few cases in which the three elements interact on an equal footing. But many regions are now striving to build eco museums that achieve this ideal balance. There are now mostly started from rural areas in the context of rich natural environment, but a few movements in urban area are very interesting because of the good participation network process. Case studies: We note and make case studies on two remarkable examples of urban eco museum movements in Japan. In Hiranocho many people take part in making their whole area museum by the way that each house or each shop display its original materials. They are all who learn each other to be a strong community. Suginami "shiruku road" is a kind of a discovery trail, which is an instructive way for inhabitants to discover their own area, and the activities encourage them to feel the local identity. And the other suburban examples of eco museums also must collaterally show these effects of community building. Conclusion: Eco museum is an idea of lifelong education or learning, of course as same as museum facility. Eco museum activities are never ending. They are constantly developed, reviewed and altered. And it is the local people who set the directions for them. The people have to be wise enough to make directional decisions in conformity with the region's identity while regularly studying the continuity of the regional environment between past, present and future. At the same time, the eco museum is supposed to be effective as an educational institution that produces such wise citizens."