The article aims to compare the thought and practice between Nammyeong Jo Sik(1501-1572), the Confucian scholar of the mid Choso˘n period and Yamazaki Ansai(1618-1682), the Confucian scholar of the early Tokugawa Japan. Most of the comparative studies are conducted to highlight the differences between the cases compared. People, for example, will expect from the comparative study of Nammyeong and Ansai's thoughts to see the differences of reception and development of the Neo-Confucian thought in Choso˘n and Tokugawa Japan. This article, however, focuses on the commonalities and similarities shared by the two Neo-Confucians who lived in the totally different political systems and backgrounds. Both of them concentrated not on how to philosophize their own thinking but on ways to actualize the truths revealed by their antecedents. Their lives, therefore, were consistent in practising the truths discovered by the sages. Their concrete methods of practice were Jing(敬) and Yi(義). The two thinkers actualized their beliefs: Nammyeong as Chushi(處士) in times of the massacre of literati in mid Choso˘n period, and Yamazaki Ansai as Binshi(賓帥) in the barrack state, a counry unfamiliar with Neo-Confucianism. They shared the common dreams of being the Wangshi(王帥) and truly corresponded to Chu Hsi(朱熹)'s idea of the citizen of the cosmopolitan world.