The purpose of this study is to investigate the topographical changes of the top of Mt. Jonam, where Haman Seongsan Fortress is located using GIS analysis (elevation, slope, aspect analysis). For this purpose, this study uses four topographic maps (1: 5,000 scale) with different timings: ① 'summit-level map based on the topographic maps of 1975', ② 'topographic maps of 1975' ③ 'topographic maps of 1996' ④ '2008 digital topographic map'. As a result of the analysis, some changes in the topographical environment were identified during the three periods, Ⅰ (? ~ 1975), II (1975 ~ 1996), and III (1996 ~ 2008). First, as a result of the elevation analysis, it was confirmed that due to natural (or anthropogenic) erosion or denudation at the top of the hill, the area ratio of the lower elevation zone was increased in the III period than in the I and II period. As a result of the slope analysis, the area ratio of the slope of 0~10 ° range decreases and then grows from the period I to II to III. This implies that hilly erosion (or denudation) prevailed during periods I to II, and artificial actions (e.g. fill, landfill), such as excavation, during the period II to III. As a result of aspect analysis, periods I and II have almost similar aspect composition. Compared to the previous periods, the III period showed a change in aspect, so that northward, northeastward, trend and southwest increased, and southeast and northwest decreased. As a result of fragrance analysis, periods I and II have almost similar fragrance composition. Compared to the previous periods, the III period showed a change in incense, increasing northward, northeast, trend and southwest, and decreasing southeast and northwest. As in the result of the slope analysis, it is thought that the artificial behavior caused the change in the slope composition during the period from the II to III.