PURPOSE: A process of mass-preparing a specific antigen used for production of an antibody which inhibits the activity of human rotavirus causing diarrhea is provided. The obtained eggs from birds immunized with the antigen have prevention and treatment effects on diarrhea. A functional food containing the egg yolk of the eggs has preventive and therapeutic effects on diarrhea in an infant and a young child. CONSTITUTION: The mass producing method of the specific antigen comprises the step of: selectively separating a gene encoding VP7 antigen by performing RT PCR using, as a template, genomic DNA of human rotavirus; extracting vector DNA by inserting the separated gene into a suitable vector, transforming a suitable strain with the vector and amplifying the vector; amplifying the gene encoding the antigen protein by performing PCR using, as a template, the extracted vector DNA; cloning the amplified gene into a suitable vector and transforming a suitable host with the vector; and culturing the host, followed by overexpressing the antigen.