It is intended to improve the water-dispersibility of a soybean 7 S protein isolate, which is rich in soybean 7S globulin as compared with a conventional soybean protein isolate, to thereby provide a beverage thereof easy to drink or ameliorate the workability thereof in producing processed food products such as dough products and tablets. The improved soybean 7S protein isolate having high water-dispersibility can be obtained by treating a soybean 7S protein fraction with an aqueous ethanol solution and drying the same followed by, if necessary, grinding or controlling the grain size. Further, the viscosity of an aqueous dispersion of the above protein isolate can be lowered by acidifying the same.