In order to improve students mathematical reasoning ability, many countries including Korea are making efforts to nurture the competence. However, no sufficient researches have been conducted on how preservice teachers, who are going to teach mathematical reasoning, understand this and which teaching capacity they should develop. Based on the consideration, this study prepared a questionnaire for preservice teachers to see what kind of mathematical reasoning knowledge they need, and provided a variety of experiences that could enhance pedagogical knowledge for preservice teachers. To see it from the students point of view, they were asked to analyze the types of reasoning utilized in solving math problems, and from the teacher s point of view, they were asked to design, practice and evaluate math classes applied with the reasoning. The results showed that the preservice teachers have improved their understanding of mathematical reasoning through various experiences and demonstrated a positive change in their ability to teach mathematical reasoning.