PROBLEM TO BE SOLVED: To provide a peptide which structurally imitates the sugar chain of ganglioside GD3, has an ability to produce an anti-GD3 antibody exhibiting cross reactivity with the GD3, and is useful as a vaccine capable of being used instead of the GD3. SOLUTION: The GD3-imitated peptide is a peptide containing an amino acid sequence represented by either of four specific sequences or a peptide containing an amino acid sequence in which one or more amino acid residues are substituted, deleted, added or inserted, and having specific bondability to the anti-GD3 antibody, and the medicine composition contains the peptide.
