This study examined the understanding the fourth- to sixth-graders of a Korean elementary school hold on war and peace. The subjects consisted of ninety children (aged 11 and 13 yrs) from the G elementary school located in Seoul. The assessment tool employed in the study was the revised version of Han`s(1989) translation of several questions from ``Young children`s understanding of war and peace`` by Tephly(1985) and ``Pre-school children`s understanding of war`` by Rodd(1985). It was composed of five and six open-ended questions related to peace and war, respectively. The homeroom teachers conducted the survey to the children. In the data-analysis, the same answers for each question were categorized and coded accordingly to the school-grade. Then a frequency analysis for each question was conduced, using SPSS18.0. Results demonstrated that the fourth-grade elementary school students held passive concepts of peace whereas the sixth-grader applied the positive concepts. Also, while the children in the fourth-grade sought external factors, the children in the sixth grade sought internal factors in the comprehension of peace and war concepts. These findings suggest that children`s understanding of peace and war differs by grade levels.