To examine the effects of knowledge use on wages, we use OECD's PIAAC data and estimate wage equations for Korea and twenty other countries. We find that, in Korea and other countries, workers' use of knowledge (skills), along with skill scores, education, and job experience, has a strong effect on wages. An increase of knowledge use by one standard deviation is associated with wage increase of 26.5% in U.K. (highest), 9% in South Korea, and 7.7% in Kazakhstan (lowest). The coefficient is significant at the 1% level in all 21 countries. These findings suggest that knowledge can affect productivity in workplaces in various ways, and that the effect of knowledge use on wages is as universal as that of skill level on wages.