Battery housing for electric vehicles plays a significant role in protecting batteries against external impacts. The risk of an electric vehicle fire, which is very difficult to extinguish, increases if the battery housing does not have sufficient structural safety. In this context, this study aims to analyze the structural safety according to the cross-sectional structure of the horizontal cross-member for battery housing in an electric vehicle against a side-impact collision. For this purpose, this study selects the battery housing of the Electric Global Modular Platform (E-GMP), which is one of the famous commercialized platforms for electric vehicles. The improvement in structural safety is analyzed according to the height and thickness of the cross member cross section. As a result, the model with the increased top thickness of the section shows a greater improvement in safety compared to models with increased side and bottom thicknesses. Moreover, the height of the cross section is observed to affect the safety improvement more than the thickness. These results demonstrate that the safety of battery housing can be improved through the cross-sectional design of the horizontal cross-member.