In recent years, practical software development exercises have been carried out in many higher education institutions. To carry out the exercises effectively, it is important that teachers understand the difficulty of learners in exercises and advise appropriately for it. Currently, a common way to check the results of the exercises is that teachers review artifacts which learners submitted. However, there is a problem in this way that it can't obtain information regarding the learners' artifacts creation process. Therefore, teachers can't fully understand difficulties of the learners. We focus on the learners' artifacts creation process and propose a method for detecting learners' difficult points during the exercises. We develop a tool that collects the class diagram creation process by learners during exercises and analyze it.