The geographical advantages of the new administrative center, Sejong city, are the major concerns for the relocation of the governmental administrative functions. The accessibility of Sejong should be prudently assessed considering social and economic factors because the previous administrative center, Gwacheon city, is much closer to the Seoul metropolitan area, the most densely populated area in South Korea. Thus, it is necessary to analyze changes in accessibilities of the new administrative center across the nation. The purpose of this study is to evaluate the accessibility from 15 regional centers for states and metropolitan cities to the new administrative city, Sejong city comparing to the previous administrative core, Gwachoen city. We analyzed the multi-dimensional accessibility of two governmental administrative cities based on the road and rail transportation network considering social and economic variables of 15 regions. The location of Sejong city is better than that of Gwacheon city for geographical accessibility from 15 regional centers. However, the accessibility of Sejong is lower than that of Gwacheon considering various factors such as population, GDP, and industries. However, the decentralization plan of governmental agencies including economic, social, and cultural factors around Seoul metropolitan areas can increase the accessibility of Sejong in the future.