This study examines legal issues surrounding the determination of authority management in mixed-use apartment buildings and explores potential solutions to the resulting conflicts. Since the introduction of Sewoon Sangga in 1968, the number of mixed-use apartment buildings in South Korea has steadily increased, leading to frequent disputes over building management. These buildings are subject to both the Multi-Family Housing Management Act and the Act on the Ownership and Management of Aggregate Buildings, causing ongoing legal conflicts between Resident Representative Meetings and Management Associations. To address this issue, this study reviews the concept of mixed-use apartment buildings and relevant legal provisions, analyzes Supreme Court precedents and legislative amendments to housing laws, and discusses key legal disputes concerning authority management. The study identifies three major perspectives: (1) exclusive management by the Management Association, (2) exclusive management by the Resident Representative Meeting, and (3) a dual management system, where the Resident Representative Meeting oversees residential areas while the Management Association manages non-residential areas. The findings indicate that, under the current legal framework, the dual management system is the most practical approach. However, conflicts between these two managing entities are inevitable. To mitigate these conflicts, this study suggests (1) establishing a joint management regulation, (2) forming a unified management association, and (3) prioritizing the application of the Multi-Family Housing Management Act to ensure legal consistency. Furthermore, the study emphasizes the necessity of legislative amendments to introduce special provisions within the Multi-Family Housing Management Act for mixed-use apartment management, thereby minimizing legal conflicts. This study provides practical insights into improving the legal management framework for mixed-use apartment buildings and contributes to a broader discussion on harmonizing public and private laws in property governance.