This article studied the concept of the expansion of the nation-wide imaginative geography abroad during the Joseon Ðynasty. 1 have looked into the case of a Tongsinsa envoy to Japan. The results are summarized as follows. First , as a prerequisite, there are two characteristics of Joseon's imaginative geography as revealed by the late Joseon' s 5jJhak scholars. One is the interaction of human geography and physical geography. The other is the interaction of ideology and practicality. Representatives of the human geography were roads and cities. The representatives of physical geography were mountains and rivers. It was to explain all of the geography of the land with these components. Also , the ideological identity was based on a feng shui geographical thought, symbolized by the Baekdu-Daegan. The practical aspect was to use a network of mountains , rivers, roads , and cities as the basis for grasping the national geography of reality. 1t also referred to the political approach and used by the kingship. Second, Korea' s identity of national imaginative geography has expanded internationally too. It was a spatial projection of historical diplomatic relations between Korea and China , called Sadae Djplomacy. 1n relation to Japan , it was a projection of the relationship between Joseon as older brother, and Japan as younger brother. The former specifically placed Kunlun Mountain , the ancestor of Chinese mountains , as well as the ancestor of Baekdu Mountain. The latter was realized by adding Mt. Baekdu as the ancestor mountain of Mt. Fuji , Japanese landmark mountain. This fact is found in the contents of the “ Haehaeng Chongjae" , records of Tonsinsa. 1n addition , special imagnative geography of Tsushima, which is located in a geopolitically obscure position as a border area, was also revealed. Tsushima was recognized as a direct reign under Baekdu - Daegan.