Because of rapid urbanization, urban green space is decreasing drastically. In order to deal with the problem, the interest in creating green space on available land is increasing. This study analyzes the economic feasibility of green roof initiatives promoted in 66 public buildings in Jung-gu, Seoul under the assumption of full financial support for green roof construction. It is proven that green roof is economically feasible with various benefits such as conserving heating and cooling energy, reducing air pollution, providing rest area, and increasing aesthetic values of city and pleasantness. In terms of this, this study identifies that the lightweight green-roof project is economically feasible with number of benefits.