The study on Yi T'oegye is one of the most delayed fields in Japan where the study on Korea generally didn’t proceed very much. The main reason is that the most Japanese researchers of Yi T'oegye have uncritically depended on the classic studies of Yoshio Abe and Susumu Takahashi. Checking the genealogy of Abe and Takahashi’s texts, it clarifies that there were three Japanese scholars who remained many texts about Yi T'oegye during Meiji period to the end of the World War Ⅱ. After the war Abe and Takahashi succeeded the three doctrines made by those pioneers and until now the doctrines are still regarded as the established theories, even though the doctrines contained lots of colonial and arrogant prejudices. This paper, therefore, indicates the various kinds of problems in the study on Yi T'oegye in modern period of Japan.