This article is about Dasuk Ryu Youngmo"s conversion. Conversion is a crucial religious category for human being called homo religiosus. Dasuk devoted his whole life to the Christian God in his lifetime. But he had a faith experience full of ups and downs and always underwent the transformation. For this reason, this article paid attention to the conversion which happened four times in his life. Especially analyzing Dasuk"s four times conversion, this study used William James" conversion theory as the framework of analysis. According to William James, our consciousness circulates between the center and the surrounding and he regards it as a conversion when the circulation is religious. In this respect the stream of consciousness of Dasuk was examined in the process of each conversion. This article concluded that Dasuk have experienced conversion four times. Accordingly based on such fact I looked through characteristic aspect of each conversion. In the first conversion Dasuk became a Christian for the first time, which was defined and examined as an adolescence conversion. In the second conversion, Dasuk moved from orthodox Christianity to unorthodox Christianity, which was explained from the James" perspective. In the third conversion, Dasuk was reborn in the bosom of his God, which was traced thoroughly in his inner side and its process. In the last conversion Dasuk went through a mystery experience, which was applied to the feature of James" mystery experience to get a scholarly approach and legitimacy. This article tried to understand Dasuk"s inner world, his life, and his thought merely. At each stage Dasuk transformed himself fiercely and through the process he seemed to reach the ultimate stage. Conclusively, each conversion was an inevitable process for him to reach the ultimate stage.