The purpose of this study is to demonstrate the effect of job satisfaction of employees on actual voluntary turnover and investigate the moderating effect of the locus of control in this process. This study differs from previous studies in several ways. First, it measures actual turnover rather than intention to leave; second, it conducts longitudinal panel analysis to overcome the limitations of cross-sectional surveys, and third, it investigates the moderating effect of the locus of control. Using the Korean Labor and Income Panel Study (KLIPS) dataset, we analyze unbalanced panel data that comprise 41,382 observations of 5,223 people. The result reveals that as job satisfaction decreases, the probability of actual voluntary turnover increases. In addition, when the locus of control is high (internal locus of control), the negative relationship between the two variables strengthens. This result confirms that job satisfaction leads to actual voluntary turnover and indicates that the negative relationship varies depending on the individual trait, that is, the locus of control. Theoretical and practical implications for individuals and organizations are provided.