Objectives: As the obesity rate has been increasing in Seoul, it is emphasized to make efforts for obesity prevention and management. The purpose of this study is to examine the effect of built environmental factors affecting the physical activity and dietary behaviors on obesity among the population in Seoul using GIS spatial analysis. Methods: GIS spatial analysis was conducted to identify the influence of built environmental factors affecting physical activity and dietary behaviors, and socioeconomic environmental factors on obesity. The data of 92,357 Seoul residents and their living environment were obtained from multiple sources and used. Results: After controlling age, sex, residential type, and officially assessed land and housing price of the study population, those who lived far from the subway station were more likely to be obese. Those who lived in the community with higher intersection density or lower steepness of the slope were more likely to be obese. In terms of the food environment, a significantly positive relationship was found between higher access to the high-calorie food and obesity. Conclusions: In order to effectively prevent and manage obesity, it is necessary to make a supportive environment to facilitate people’s healthy behaviors through multidisciplinary and multi-sectoral efforts.