This paper aims to analyze the wage gap between regular and non-regular workers according to the wage distribution in South Korea. In South Korea, there are various types of non-regular workers, and there exists a distinct labor market separation between regular and non-regular workers. In addition, the proportion of non-regular workers in total employment is high, and the wage gap between regular and non-regular workers is steadily increasing. This paper estimates the wage gap between the two groups across the wage distribution using the unconditional quantile regression model (UQR) in order to overcome the limitation of estimation by OLS, which only focuses on the average of wage distribution. Then, we decomposed the wage gap into the explained part caused by the difference of productivity and the unexplained part to estimate the size of discrimination. As a result, the wage premium for regular workers differs according to wage distribution, and it has a relatively strong negative effect under low wage distribution. Moreover, as a result of the decomposition of wages, we identified that the size of the discrimination against non-regular workers increases in upper wage distribution.