This paper analyzed the effects of national development and decentralization policies on the regional income disparity in Korea. It also attempted to test whether there was a structural change in the causal relationship between income inequality and its determinant factors. This study found that the degree of variation in regional incomes was positively correlated with the spatial distribution of decentralization instruments such as educational services, employment, infrastructure facilities, and information network variables. The effects of some decentralization policies on regional income inequality were fully realized within a period of three years. Finally, the impacts of the spatial decentralization of public goods on regional inequality fluctuated until the early 1980s but were stabilized as industrial restructuring and spatial reorganization progressed during the 1990s.