The present invention provides novel antigens of an allergy to soybean, methods and kits for diagnosing an allergy to soybean, pharmaceutical compositions comprising such an antigen, soybeans or processed products of soybean in which such an antigen is eliminated, and a tester for determining the presence or absence of a soybean antigen in an object of interest. The present invention also relates to polypeptides comprising an epitope of an allergen, kits, compositions and methods for diagnosing an allergy, comprising such a polypeptide, pharmaceutical compositions comprising such a polypeptide, and food raw materials or edible processed products in which an antigen comprising such a polypeptide is eliminated or reduced, or the polypeptide is cleaved or removed. The present invention further relates to a tester for determining the presence or absence of an antigen in an object of interest.