It is aimed at developing a novel method of fractionating 7S globulin and 11S globulin, in particular, a highly accurate and efficient fractionation method which can be performed on an industrial scale. It is also intended to obtain a protein fraction which is little contaminated with oil-body-associated proteins and exhibits the characteristics inherent to highly pure 7S globulin and 11S globulin. A process for producing soybean protein characterized by comprising heating a solution containing soybean protein to 30 to 75.degree. C. under acidic conditions of pH 3.8 to 6.8 and then fractionating it into a soluble fraction and an insoluble fraction at an ionic strength of 0.02 or more and a pH value of 4.5 or higher but lower than 5.6.