Defects in apartment buildings significantly impact the convenience and safety of residents, and their prevalence has been steadily increasing. This study prioritizes the key defects in apartment buildings to enhance quality management. The primary causes of defects were identified by focusing on frequently occurring issues such as tile installation, flooring, wallpaper, PL windows, and kitchen furniture. A literature review was conducted to analyze the main types of defects, and expert focus group interviews were held to investigate the causes of defects and potential countermeasures. Following this, the analytic hierarchy process was employed to assess the relative importance of these defects and establish their prioritization. The findings indicated that structural issues and material-related factors, particularly flooring and window installation, were the primary causes. Based on these insights, this study proposes a strategic approach to improving quality management in apartment buildings. This research serves as a valuable reference for developers, contractors, and policymakers in defect prevention and management.