Uiam Ryu In Seok was born in Chuncheon, Gangwon-do in 1842, in the late Joseon Dynasty. He went through a period of chaos in reign of potentates, and lived a period of upheaval called Japanese colonial era. In the late Joseon Dynasty, he early went under the leadership of Hwaseo Lee Hang-ro(華西 李恒老), one of the three great philosopher of Juri(主理) philosophy, and studied hard. And during the period of mayhem, he dedicated himself to saving the people and the country. As an Confucian scholar, he was the head of the righteous army who led the anti-Japanese army, and during Japanese colonial era, he worked as an independence activist. He left a great mark on the history of Confucius in Korea and the history of anti-Japanese righteous army. He did the movement of Wijeongcheoksa(衛正斥邪) against Western aggression and devoted himself to the anti-Japanese righteous army movement and the independence movement, so he did not have time to take proper care of himself and his families. Naturally, he could not afford to accept a position as a public official. Like his teacher, he did not go to the public office through Gwageo tests(科擧). He was not a public official like this, but his integrity, a key virtue of public officials, was extraordinary. Nevertheless, there is not much research on his thought of integrity. That is why it is worth studying his thought of integrity. There is a clear reason to study his integrity, a key requirement for public officials. He was born and lived in the late Joseon Dynasty and the most chaotic and difficult times in Korean history, but he practiced the thought of integrity all his life. Integrity means 'nobility and lack of greed'. There are many conditions for integrity. But the most important of them are loyalty, sincerity, filial duty, innocence, frugality, benevolence, justice, virtue etc. It is no exaggeration to say that Ryu In Seok's life has all these things. These thoughts of his integrity can be summarized as loyalty, filial piety, benevolence, and frugality. He has been very filial since he was a child. He loved his neighbor and gave love to people he didn't know very well. It extended this filial piety to the country. That is loyalty. Finally, he lived a frugal and restrained life all his life, avoiding material and external things such as wealth, women, and alcohol. His thoughts of integrity greatly influenced the independence movement. Although he died in 1915 without seeing the independence of Joseon, he still lives and breathes in the spirit of the Korean people, and still teaches integrity. In this way, the thought of Ryu In Seok's integrity is still shining brilliantly. His thought of integrity is making our society fairer and cleaner. We hope that research on the integrity of Ryu In Seok will be more active in the future.