We have developed a system called "Web-Com" forWebbased education: the Web browser provides a multi-layer drawable canvas on which users can draw annotations on Web pages. Annotations can be shared with other users in real-time and non-real-time for use of synchronous and asynchronous learning. This paper mainly discusses the asynchronous function including processing of annotation by recorded voice. That is, it can replay the process of annotations including the process of voice recording, which enables asynchronous learning. In our previous work, we conducted a subject experiment to evaluateWeb-Com?s synchronous functions. The experimental results showed that the learners could learn fairly interactively with an instructor in a Web-Based class. In this paper, we conducted a subject experiment in an actual class, to evaluate its asynchronous functions and validity of asynchronous learning. The experimental results indicate that Web-Com has advantages for the learners to understand given lectures.