Gross National Product(GNP) represents the market value estimates of economic welfare gained from goods and services purchased in the market and consumed by the people. Due to the extraordinary development of the national economy in recent years, however, not only have production and income levels been promoted, but also troubles emanating from more and more complicated socio-economic structures have been intensified as well. Welfare-impending factors such as environmental pollution, traffic accidents, etc., have subsequently appeared. Under these circumstances, an attempt was made to establish a new indicator of economic welfare, ISEW(Index of Sustainable Economic Welfare), by of modifying the present national income concepts. This paper produced the estimated value of Welfare GNP in Korea by adopting the concept of ISEW.