According to the invention, immunogenicity of an antigenic peptide is increased by administering a fusion protein, which comprises an antigenic peptide and an adjuvant protein, wherein the adjuvant protein comprises two or more proteins selected from the group consisting of a Shiga toxin 2e B subunit (Stx2eB), an Escherichia coli heat-labile toxin B subunit (LTB), and a cholera toxin B subunit (CTB). or a transformant transformed by a gene coding for the fusion protein.
