Many studies have investigated the process of rule discov- ery. However, the data utilized in these studies, such as per- formance and verbal protocol data, were course-grained. In this study, we designed a new experimental method using eye movement data to observe the detailed process of rule discov- ery. In the proposed method, we corresponded the task display and a rule space in the participants’ minds to understand how they consider the rules and observe instances by eye tracking. Then, we compared the process of rule discovery by people with high and low working memory capacities. The results of the experiment revealed that those with high working memory capacity tried to consider one or similar rules from multiple instances. On the other hand, those with low working memory capacity tended to consider various rules from one instance.