This paper explores the ‘scientific’ transformation of ideas on traditional Korean medicine focusing on Cho Hŏnyŏng and Kim T’aejun’s Debates in newspapers in the 1930s. After confronting Western medicine, traditional medicine had been developing and institutionalized in different ways and shapes in East Asia. In this process, scientizing traditional medicine was the priority task. However, if traditional medicine had to confront and adjust themselves to so-called ‘scientific’ Western medicine, was it about the layer of methodology or even reach the theoretical layer? The debates between Cho Hŏnyŏng and Kim T’aejun show the hazy lines of this discourse. Kim set aside the yin yang theory from traditional medical practice and tried to absorb it to the ‘scientific’ theory and methodology, which means a materialistic view in his context. On the other hand, Cho didn't deny Kim's theory and methodology but rather tried to compromise traditional medicine thoughts and Western knowledge. Cho believed that it could be possible to explain and yin yang theory in a scientific method. Through the conversations between the two, the complex meaning of ‘scientific’ was revealed, and was possible to see the one side of the discussion of 'what is scientific' to traditional medicine. The scientization of traditional medicine in Korea was carried out in two areas, the theoretical and practical dimensions, respectively, or simultaneously. The series of debates between Cho and Kim can shed a light on the various ways of scientization and the different junctions where traditional medicine in East Asia headed after