This paper examines the evolution of inter-organizational relationships between vehicle body assemblers and battery manufacturers for battery electric vehicles from the perspective of R&D and business strategy. With the rapid global shift toward BEVs, Japanese automotive companies must rebuild and seek new inter-organizational relationships, while still focusing on traditional inter-organizational relationships (cooperative companies). Meanwhile, new entrants to the BEV battery market are actively pursuing global strategic alliances with automotive firms to expand their overseas production bases rapidly. In this study, we use social network analysis to visualize the evolution of inter-organizational relationships among BEV battery companies in a dynamic and multifaceted manner and contribute to the proposal of effective R&D and business strategies for Japanese automotive companies and others.