A new lecture supporting system based on real-time learning analytics is proposed. Our target is on-site classrooms where teachers give their lectures, and a lot of students listen to teachers' explanation, conduct exercises etc. We utilize not only an e-Learning system, but also an e-Book system to collect real-time learning activities during the lectures. The proposed system is useful for a teacher just before lecture starts and during the lecture. The system provides summary reports of the previews of given materials and quiz results. The teacher can check which pages were well previewed and which pages were not previewed by students using the preview achievement graph. Additionally, the teacher can check which quizzes were difficult for students, and the suggested pages that should be explained in the lecture to aid students. During the lecture, real-time analytics graphs are shown on the teacher's PC. The teacher can easily grasp students status whether or not students are following the teacher's explanation. Through a case study, we confirmed the effectiveness of the proposed system, in terms of high synchronization between a teacher and students, i.e., the teacher adjusted the speed of his lecture based on the real-time feedback, and many students followed the teacher's explanation.