One of the perspectives to analysis mathematics classroom is to investigate teacher's metacognitive activities. The purpose of this study is to construct the framework of teacher's metacognitive activities underlying mathematics teaching and to analyze the characteristics of teacher's metacognitive activities. Then it is able to create the program of teacher education on the basis of teacher's metacognitive activities. For the purpose of this study, this article proposed the framework to investigate teacher's metacognitive activities, on the basis of Artzt & Armour-Thomas (2001). To put it concretely, firstly teacher's metacognitive activities were compared with metacognitive activities on mathematical problem solving. So teacher's metacognition has two aspects, metacognitive knowledge and metacognitive skill. Especially this article focused on teacher's metacognitive skill that is consisted of monitoring, self-evaluation and regulation. Secondly, it makes clearer understanding about teacher decision making to investigate teacher's metacognitive activities underlying mathematics teaching. Using the framework to investigate teacher's metacognitive activities, two mathematics instructional practices were analyzed. As the results of these practices, the following metacognitive activities were founded. The teacher monitored students' comments and activities, reflected some contents that students' had already learned.
