There were a lot of attempt to reform mathematics education. These may include reforms of teaching and learning methods, development of mathematics curriculum and textbooks, materials and resources for teaching. But the most important thing is reform of teaching and learning method. The teaching and learning in mathematics is related with culture of mathematics classroom. Thus the culture of mathematics classroom plays a critical role in the learning of mathematics. Although there is consensus what desirable culture of mathematics classroom is, the role of teachers is important to make desirable culture of mathematics classroom. So, this paper suggested the role of teachers in reforming the culture of mathematics classroom. Avoiding from routine and technical teaching, the teachers should play active role in constructing mathematical understanding of students.