In this paper, I emphasized that empirical studies are significant in terms of particularities and specific purposes of history education research. Based on this idea, I reviewed a series of research of how students understand history and investigated the meanings and implications of these empirical studies. Before 1980s, studies of students’ historical understanding focused on evaluating students’ cognitive abilities grounded in Piaget’s theories of developmental stages. Since 1980s, however, with a wide range of critiques toward Piaget’s theories as well as introductions of constructivism, studies have tried to understand how students interact with history. In this study, I categorized empirical studies conducted after 1980s in three different fields: 1) Students’ understandings of historical contexts, 2) students’ reliance on historical narratives, and 3) students’ approaches to sources and historical inquiry. I, then, stressed that empirical studies help history educators grasp students’ historical thinking and understand what students can do with history. Eventually I argued that history educators need to actively conduct empirical studies on students’ historical understanding, and the results of empirical studies should be the basis for the discussions of history curriculum and instruction.