This paper adopts a distributive performance process model of in-work poverty based on labor markets, households, and welfare states and analyzes the 4-11 waves of the Korean Welfare Panel Study during 2008-15. Previous studies on in-work poverty have focused on the definitions and concepts of in-work poverty by analyzing employment and unemployment persistence and repetition dynamics, but rarely paid attention to institutional distributive performance. In this regard, this study preforms a stepwise analysis of labor markets, households, and welfare states as a process of income generation in labor markets, satisfaction of welfare needs and income pooling at households, and deduction of social security contribution and income tax as well as receipt of public transfer income at welfare states. Results of empirical analysis show that in-work poverty had been on increase during 2008-11, followed by a decrease between 2012-15. At labor market stages, full time status had the most prominent impact on in-work poverty process, while status by employment and contract type have generated a huge variation as well. At household stages, household work intensity and number of earners contributed to reduction of in-work poverty, but the relations did not seen to be straightforward. However, welfare state played little role in lifting employees out of in-work poverty. In terms of institutional distributive process, in-work poverty was prevalent in either household-welfare state stage or labor market-household-welfare stage. Non-vulnerable group in terms of in-risk poverty was around 80% of the sample during the period of analysis, the size of which has remained constant.