The present invention provides a synthetic peptide whereby antibodies to an autoantigen can be derived, and specifically provides: a multiplex alloantigenic peptide including a dendritic core and a B-cell-recognition peptide, the multiplex alloantigenic peptide including four to eight B-cell recognition peptides of the same type bonded directly or via a spacer to a terminal end of the dendritic core, the peptides being bonded directly or via a spacer to the terminal end of the dendritic core； an antibody production inducing agent including the peptide； and a method for producing the peptide.
