Today, negative perceptions of overwork are spreading, and it is also becoming an important social issue. Many prior studies suggested that overwork negatively affects job satisfaction and quality of life, but the debate about the sub-factors of overwork is relatively insufficient. Therefore, this study presents sub-actors such as time, allowance and decision of overwork, and used data of ‘Korean Labor and Income Panel Study (KLIPS)’ conducted by Korea Labor Institute to analyze the effect on job satisfaction. As a result of analysis, time and allowance of overwork do not affect job satisfaction, whereas the decision of overwork has a positive effect on job satisfaction. In other words, if overwork can be decided at the discretion of the individual, it can be explained that job satisfaction is enhanced. The results of this study can be used as basic data for discussions related to overwork in the future, and it is meaningful in that it analyzes detailed factors of overwork.