The teacher's gaze attention can trigger interaction with the student. So if the teacher fails to equal attention during class, students may be alienated from the interaction. According to this perspective, this study aimed to establish the pattern of the teacher's gaze during science lecture classes and whether the change of the gaze when the student's seat as an external factor changed. Eye tracking was conducted on six teachers during class, and the teacher's gaze fixation and movement were also analyzed after changing the student seat. According to the results, teachers mainly focused on the center of student seats, and the gaze blind spot was mainly biased forward. Even if the student's seat was changed, the gaze was focused on the center of the classroom, and the gaze blind spot differs within the individual, and the teacher tends to be unaware of it himself. Consequently, the teacher's gaze concentration pattern is generally similar, but the gaze blind spot varies depending on the teacher and can be affected by external factors. Therefore, it is necessary to develop a system and retrain program for diagnosis and feedback of teachers' attention to provide proper and high-quality education to students.