This study explores the effect of corporate social responsibility (CSR) on customer-based brand equity. Many studies investigates the effect of CSR on consumer attitude and behavior intention such as brand attitude and purchase intention, but few directly explores the effects of CSR on brand equity. It is meaningful to explore the role of CSR as a prior variable in building brand equity as building brand equity is one of the purposes of marketing communication. It uses indices that are measured by third parties, such as KEJI and K-BPI as variables for CSR and customer-based brand equity respectively. KEJI consists of six-dimensions including soundness, fairness, employee satisfaction, consumer protection, social contribution, and environmental management, and K-BPI is measured based on consumer awareness and loyalty. Based on stakeholder theory, CSR is divided into two types: internal and external CSR that are targeted at internal and external stakeholder respectively. Then it explores the differences in influence between the two types. Research has shown that external CSR composed of three dimensions: consumer protection, social contribution and environmental management significantly affects customer based brand equity. However, it is found that the internal CSR comprised of the soundness, fairness, and employee satisfaction does not have a significant impact. In addition, the effect of external CSR on customer based brand equity is greater when using the corporate brand dominant strategy (the corporate brand is used for individual product) when the CSR is running at the corporate level. This study shows that CSR activities, particularly targeting external stakeholder, can be significant prior variables in building customer-based brand equity. Furthermore, it suggests that a strategy should be used to link the CSR to the individual brand in order to use CSR as a more effective marketing communication.