Recent urban sprawl has destroyed various kinds of green space in the city. It has affected quality of people’s life in the city, as well as urban ecosystem. Recent study shows the possibilities of roofs as green spaces in urban central site where the land costs are generally high. This research focuses on Jung-Gu district in Daegu Metropolitan city as a study area and calculates possible area of green roof using 2002 Autocad program based on aerial photographs and land registration maps. And the purpose of this research is to analyze environmental and economic effects of green roof. The environmental effects are as follows. It is expected that 91,106 ㎡ green spaces, 12.13 % of study site, will be added if green roof is performed in the study site. It is assumed that the expanded areas could reduce the highest temperature to 0.5-1.0 ℃ during the summer in terms of environmental effect. And the following shows the economic effects. If green roof and greening urban central site are created as a same size of 91,106 ㎡, it will be expected that the costs of green roof will be much more inexpensive than about 98 billions won. It will be also found that the expense of cooling energy can be saved out about 8 millions won per day in summer, if grass planting is accomplished on the possible areas of green roof in the study site. Therefore, it is desirable to take legal supports such as enacting regulations to activate green roof for more environmental and economic effects. For instance, green roof for public institutions, school and model area selection are desirable method to publicize the effect of greening program for citizen's participation.