Contents of phenolic compound including isoflavones and phenolic acids as well as antioxidant effects in high-protein soybean cultivar "Saedanbaek" were evaluated under different roasting conditions. The roasted soybean exhibited significantly higher antioxidant activity than unroasted soybean in the three antioxidant methods including 2,2-diphenyl-1-picrylhydrazyl, 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid), and Ferric reducing antioxidant power. In particular, the roasted soybean at $200^{circ}C$ for 15 min showed the highest antioxidant activity in comparison with other conditions. The contents of phenolic compounds, isoflavone aglycones (genistein, daidzein, and glycitein), isoflavone ${eta}$-glucosides (genistin, daidzin, and glycitin), and phenolic acids increased, whereas isoflavone malonyl-${eta}$-glucosides decreased during roasting process. Moreover, total phenolic and flavonoid contents as well as those of isoflavone aglycones, isoflavone-${eta}$-glucosides, and phenolic acids increased, leading to a general increase in antioxidant activity after roasting. These results suggest that the roasting soybean extracts could contribute to obtaining natural antioxidants in certain food applications.