These days, according to the increasing interests in 'reflection' in teacher education, the study about a teacher as the reflective practitioner is going on variously. Reflective teaching is the essential and basic characteristic of a teacher. As the relationship between teachers' reflective teaching and development is acknowledged, the assertion is expanding that teacher education focuses on the development of the teacher's reflective thinking. However, although a number of researches acknowledge the importance of 'reflection' and 'reflective teacher education,' they are highlighting only the implication of 'reflection' on the teacher's profession or the teacher education, overlooking the ambiguity of the notion, `reflection.' So the reflective thought is interpreted as a subject that should be taught or a sort of strategy that a teacher should learn, while the aspect is excluded that reflection is the interaction between the innate knowledge and the practice. As a result, on the basis of various notions of reflection, the reflective teacher education programs that increase the level of reflection are developed and practiced, and the reflection is accepted as a tool for increasing teacher professionalism. In this article, as a device of reflective teacher education, the meaning and the role of 'reflection' is surveyed in the course of pedagogical reasoning exposing teacher's Pedagogical Content Knowledge(PCK). First, the meaning of Sch?n's reflection is examined. Second, Shulman's pedagogical reasoning and action is examined and the meaning and the role of 'reflection' are considered on the course of revealing PCK. Third, new commentary of reflective teacher education is considered, analyzing the role of reflection and the meaning of PCK in 'Reflective Teaching Model' on the basis of reflections of two mathematics teachers in the middle school and their class improving cases.