This paper basing on Japanese learning books of the Chosen Period has the purpose of giving a report on the actual condition of the confusion of the 'Yotsu-Gana' that appear in these materials and the application of it on the history of the Japanese language. Research on the confusion of the 'Yotsu-Gana'is almost solely based on Kana materials, Christian materials or Chinese materials, leaving out a comprehensive research from Korean materials. The approach of one more aspect, namely Korean materials, cannot be left out from the research on the actual condition of the confusion of the 'Yotsu-Gana'. A new approach from this angle will give an opportunity to reconsider already existing various accounts, and at the same time it will give abundant sources to approach the problem of the confusion
