The paper investigates medical missionaries that exerted a significant role in establishing Western medicine in the late nineteenth century Chosun in relation to orientalism an academically popularized concept introduced by Edward Said Historical analysis is focused on several important medical missionaries such as Horace N Allen William B Scranton John W Heron C C Vinton and Oliver R Avison to explain how their activism as medical missionary contributed to the formation of medical orientalism in which Western medicine was ´taught studied administered and judged´ in that period In addition I explore into how medical orientalism was in service of Japanese imperialism by showing that medical missionaries had to be under imperial surveillance by Japanese colonizers article explores the medical system of the Koryo Dynasty period and its social characteristics First the structure of medical system and roles of medical institutions during the Koryo Dynasty period will be summarized Then the characteristics of the medical system will be identified through exploring the principles of its formation in a view of social recognition of medical care and a view of public policy.