A new soybean cultivar ‘Wonhyun’, was developed by mutation breeding technique using a 250 Gy gamma ray at Korea Atomic Energy Research Institute (KAERI) in 2010. ‘Wonhyun’ has black seed coat and much better agronomic performance than original variety ‘Paldal’. Their total yield (177.1kg/10a) is much higher than that of ‘Paldal’ (126.9 kg/10a). Also, 100 seed weight of Wonhyun was 27g compared to ‘Paldal’ (13.7g). Contents of 4 essential amino acids such as aspartic acid, glutamic acid, lysine, arginine and unsaturated fatty acid including linoleic and linolenic acid have much higher than ‘Paldal’. This cultivar is good for cooking with rice as improved functional ingredient soybean.