At present, we need to establish the terminology of ‘The West Sea'. Historically, The West Sea was a channel for China-Korea relations, Namjo-Baekje, Tang-Chunghaejin. Therefore, the West Sea was the area of maritime activities in Goguryeo, Baekje, Goryeo, and Chosun. The term ‘The West Sea' is a historical term used from ancient times to the present. Therefore, even if we use it now, there is no problem at all. Meanwhile, from ancient times to the empire, the term ‘The Yellow Sea' has never been used in our history. The ‘The Yellow Sea' emerges from Thomas Jeffries' Asian highlands around 1748. With the introduction of Western maps and mapping techniques in the Chung Dynasty, the ‘The Yellow Sea' began to be translated into Chinese characters ‘The Yellow Sea'. Therefore, the present “Yellow Sea” is an alias of West Sea created by Westerners. Similarly, in the case of the ‘Joseon Sea' appearing in the Joseon Dynasty at the end of the nineteenth century, ‘Sea of Corea' is emerging in Thomas Jeffries' Asian Highlands around 1748.