Provided are a method of concentrating protein in grain powder, grain powder including protein that has been concentrated by using the method, and a feed additive including the grain powder including concentrated protein. According to the method of concentrating protein in grain powder, grain powder is treated with enzyme to increase the water-soluble saccharide content in a source, and by inoculating bacteria or yeast and fermentation, the increased water-soluble saccharide is removed, leading to a higher concentration of protein. Thus, the protein content ratio increase effects and the function of grain powder as a protein source are enhanced.
