Cho Sik was a great scholar in Chosun Dynasty. He was a contemporary scholar with Lee Hwang. We can see some statements of Cho Sik in the books written by Lee Ie(Yoolgog). It is obvious that his thoughts affected many scholars later. In addition to this, he taught many disciples some of whom became public officials, and some became civil leaders in the War named Imjinwoeran(the invasion of the Japan, 1592). His administrative thoughts are revealed in the Letters to the King(Sangso) more clearly. And so the author analyzed the Letters and classified his administrative thoughts. The findings were like these. His administrative thoughts could be summed 4 suggestions : leadership, personnel administration, administrative ideologies(the administration for the people and Minbon/民本 thoughts), the listening of public opinion, and the timing and Hersil(虛實, formal/substantial) as criteria for policy-making. His administrative thoughts belong to the style of Moral-training - oriented mentioned in the paper. Generally speaking, we can see that Cho-Sik emphasizes most the Moral-training of the leader and the recruitment based on that. The administration for the people and Minbon thoughts also are the ideologies for the leader. The listening of the public opinion and the criteria for policy-making wholly rely on the will of the leader. It follows that we can see that he suggested Moral-training and will of leader for the solution of the bureaucratic problems, and he rarely discussed practical systemic and institutional reforms. This seems to reflect his absence of practical experience as a public service in bureaucratic system. Nevertheless, his thoughts affected many practitioners and scholars later. And so we need to study the relationships with them and effects on them more clearly.