This paper examines how the status and function of the Gae'seong city, the former capital of the Goryeo dynasty, changed after the fall of Goryeo. The Gae'seong city in the early days of the Joseon Dynasty, which has actually never been properly discussed, will be examined here. How Gae'seong obtained its status as a city with an important history after the foundation of Joseon, and how the urban side of this city developed during the dynasty's early days, will all be examined here. The nature of this study differs from those of previous studies, as it primarily deals with certain changes that occurred during the early days of Joseon, with a focus upon urban historical perspectives. Gae'seong had been the political and commercial center of the Goryeo dynasty and also the Korean peninsula for a very long time, yet when Han'yang became the new capital, Gae'song was no longer able to hold its previous position as a political center. Gae'seong became a city (a) important for [only] commercial activities and consumption, (b) through which envoys passed on their way to Ming on diplomatic missions, (c) that had played a significant role in the foundation of the Joseon Dynasty, and (d) where the Royal tombs of the Joseon royal family members remained. In the early days of the Joseon dynasty, Gae'seong continued to change rather slowly, and departments of Yuhu-sa and Yusu-bu were created. They were in charge of the administrative governing of Gae'seong. Gae'seong's character was strong, as the No.2 capital of the dynasty and also the kings' own home town until the reign of King Taejong. However, from the time of King Sejong, these characteristics diminished, and the old attributes as the 'previous capital' were strengthened. Also, Gae'seong became a major traffic point for the foreign diplomatic envoys that were headed for the Joseon capital, and functioned as a major regional commercial city, second only to the city of Han'yang.