Kim, young ok. 2019. A study on 'masu' in Japanese language textbooks during the Chosun Dynasty. Language Information 28. 25-39. This study examines how Japanese honorifics which are one of the first things to learn in modern Japanese were used, focusing on ‘masu’ in Japanese textbooks between the 15th and the 18th century. I checked its change in Japanese language history and compared it with that of the Japanese and Christian data. In the 15th century book “Iroha”, ‘masu’ was not seen but a honorific ‘soro’ was commonly used. As of the 17th century, ‘marusuru’ first appeared. After the latter half of the 17th century, before the middle of the 18th century, it changed into ‘masuru’ and modern type of ‘masu’ is also seen. The changes of ‘masu’ in Japanese language history are well known in Japanese textbooks. In addition, ‘marusuru’ is found in Japanese textbooks which was typically used at that time but was not recorded in the Japanese data and the Christian data because it is a slang.