This paper searches for how Ryukyu recognized Joseon Korea, basing the analysis on diplomatic documents of Ryukyu. Ryukyu exchanged diplomatic documents written in Chinese characters with East Asian nations from 1372, and the Rekidai Hoan was printed in 1697 after the compilation of the diplomatic documents of Ryukyu. An important change appeared in the style of the diplomatic documents of Ryukyu. By 1400, the King of Ryukyu sent to the King of Joseon a formal letter that established the documents of friendship. It was confirmed in the Taejong Sillok, the annals of King Taejong, that from 1409 the style of documents was changed to the jamun(咨文), a kind of submission document. This was the first case among the diplomatic documents compiled in the Rekidai Hoan that the King of Ryukyu sent the jamun to the King of Joseon, in 1431. In this way, Ryukyu’s sending the jamun to Joseon meant that Ryukyu intended to reveal on purpose that Ryukyu was positioned in an equal relationship with Joseon diplomatically. But it can not be said that Ryukyu was entertained as an equal with Joseon in practice. Considering the level of treatment with Joseon and Ryukyu in China, it was clear that Joseon was higher than Ryukyu. Further, Ryukyu sent the jamun to Joseon, meaning an equal relationship, but Joseon answered by sending the seogye(書契) document. That is, it can be asserted that Joseon refused Ryukyu’s demand of equal relationship between the two nations.