This study was done to determine the effect of additional nitrogen fertilization on the yield and quality of the Korean wheat cultivars Keumkang, Jokyoung, Baegjoong, Sooan, Uri and Goso. Different levels of nitrogen applications (109, 82, 55, 41, and 27 kg/ha) were applied to six cultivars. The results show that the yield and protein contents were increased in all tested cultivars. The grain yields of the cultivars Keumkang, Jokyoung, Baegjoong and Sooan were greatly increased in the case of double fertilization treatments. Moreover, Uri and Goso had greatly increased yields by the additional fertilization at a 50% rate compared with korea wheat standard fertilization rate. A significantly higher yield was observed in Uri. Baegjoong was the highest yielding cultivar among the tested cultivars with the additional nitrogen fertilization. As the fertilization was increased up to double the fertilization treatment, the yield of Baegjoong also showed a constant increase. Positive correlations were found between the nitrogen fertilizer application levels and the protein contents of the grain in all the cultivars except for Uri, and among these, Jokyoung had a most significant correlation between the nitrogen fertilizer application level and the increase in its protein contents. Keumkang had the highest protein contents and highest increase in the protein content change according to the amount of nitrogen application. However, amylose, damaged starch and ash contents were not significantly changed by the different levels of nitrogen applications.