After Japanese Invasion of Korea in 1592 was over and the situation was coped with, Chang-Kyoung Palace and Chang-Duk Palace were rebult, and In-Kyung Palace and Kyung-Duk Palace were built during the reign of Kwang Hae Kun. Many utilitarians were engaged with the construction as a manager, and they devoted themselves to improve technology. As a result, craftsmen were treated so valuable, compared to the past, that they were consulted about the technical problems under construction, the process of making an estimate, and the management of construction materials. Moreover, famous craftsmen obtained the government service. And there were various attempts on organizing and compensating workmen in order to manage them efficiently. In addition, the know-how of manufacturing a blue tile, which had been failed to succeed due to the war, was revived, and manufacturing a yellow tile, which had not been used, was studied by utilitarians. Finally, There were many kind of technical attempts and development under the construction of palaces, which gave utilitarians a chance to express their ideas, expected practical science, and assembled craftsmen who had scattered due to the war, during the reign of Kwang Hae Kun