The present invention relates to a method for analyzing the content of 11S (glycinin) and 7S (β-conglycinin) proteins in soybeans using RP-UPLC. The method according to the present invention provides optimal RP-UPLC conditions enabling efficient, high-resolution, and highly reproducible analysis of soybean 11S and 7S proteins and subunits thereof. Accordingly, the present invention provides qualitative and quantitative information on 11S and 7S proteins to select soybeans that can be effectively used in processed foods using soybeans such as meat alternatives, tofu, and soymilk, and can thus be effectively used in the manufacture of processed foods using soybeans.