The main purposes of privatization in many countries are the need to control government spending in the emergence of a tight fiscal environment, to improve efficiency of public firms, to increase investment in social infrastructure sectors and to access new opportunity of developing financial markets. This paper analyzes after-privatized operational efficiency of 7 public firms that privatized between late 1990s and early 2000s in Korea. We use Wilcoxon rank sum test and difference-in-differences model to test the differences of firms' profitability, efficiency, leverage ratio, growth and employment level before and after privatization. We find that privatization improves firms' profitability, growth and efficiency in both method. While we find that debt ratio decreases based on Wilcoxon test, difference-in-differences model shows that there is no significant change of debt ratio after privatization. Only failing public companies may decrease their debt after privatization but it is not that significant. The general hypothesis that privatization decreases firms' employment level may not be supported based on our empirical analysis.