In this study, we propose an evidence based approach to improve web-based teaching materials based on access logs of students using the materials. In this approach, the web-based teaching materials are evaluated based on the following data: (1) students' learning pace, (2) their activities of referring help items, and (3) students' questions to teaching assistants. We evaluated the utility of this approach by using the data in university classes for freshmen. As a result, we confirmed the following points: the improvement of the materials based on this approach actually reduced the number of questions to the teaching assistants, and also reduced and the number of slower-paced students.
