An antigen peptide specific to cancer stem cells represented by Y 0 -X 0 -Z 0, wherein X 0 is any one of to below: a partial peptide of an ASB4 protein, wherein the amino acid sequence of the partial peptide consists of an amino acid sequence represented by any one of SEQ ID Nos: 3 to 7, 9 to 11, 13 to 19, 21, 22, 26 to 28, and 30 to 46; a peptide which, in the partial peptide defined in, the second amino acid from the N terminal being replaced by leucine, isoleucine or methionine, and/or the amino acid at the C terminal being replaced by valine, leucine or isoleucine; a partial peptide of the ASB4 protein, wherein the amino acid sequence of the partial peptide consists of an amino acid sequence represented by any one of SEQ ID Nos: 3, 5 to 7, 9 to 14, 16, 19, 21, 22, 24 to 26, 28, 30 to 32, 34 to 37 and 39 to 46; or a peptide which, in the partial peptide defined in, the second amino acid from the N terminal being replaced by tyrosine, phenylalanine, methionine or tryptophan, and/or the amino acid at the C terminal being replaced by leucine, isoleucine or phenylalanine; and, Y 0 and Z 0 are mutually independently a peptide consisting of 0 to one amino acid or the entire Y 0 -X 0 -Z 0 consists of a partial peptide of the ASB4 protein represented by any one of SEQ ID Nos: 8, 20, 23 and 29. X 0 is any one of to below: a partial peptide of an ASB4 protein, wherein the amino acid sequence of the partial peptide consists of an amino acid sequence represented by any one of SEQ ID Nos: 3 to 7, 9 to 11, 13 to 19, 21, 22, 26 to 28, and 30 to 46; a peptide which, in the partial peptide defined in, the second amino acid from the N terminal being replaced by leucine, isoleucine or methionine, and/or the amino acid at the C terminal being replaced by valine, leucine or isoleucine; a partial peptide of the ASB4 protein, wherein the amino acid sequence of the partial peptide consists of an amino acid sequence represented by any one of SEQ ID Nos: 3, 5 to 7, 9 to 14, 16, 19, 21, 22, 24 to 26, 28, 30 to 32, 34 to 37 and 39 to 46; or a peptide which, in the partial peptide defined in, the second amino acid from the N terminal being replaced by tyrosine, phenylalanine, methionine or tryptophan, and/or the amino acid at the C terminal being replaced by leucine, isoleucine or phenylalanine; and, a partial peptide of an ASB4 protein, wherein the amino acid sequence of the partial peptide consists of an amino acid sequence represented by any one of SEQ ID Nos: 3 to 7, 9 to 11, 13 to 19, 21, 22, 26 to 28, and 30 to 46; a peptide which, in the partial peptide defined in, the second amino acid from the N terminal being replaced by leucine, isoleucine or methionine, and/or the amino acid at the C terminal being replaced by valine, leucine or isoleucine; a partial peptide of the ASB4 protein, wherein the amino acid sequence of the partial peptide consists of an amino acid sequence represented by any one of SEQ ID Nos: 3, 5 to 7, 9 to 14, 16, 19, 21, 22, 24 to 26, 28, 30 to 32, 34 to 37 and 39 to 46; or a peptide which, in the partial peptide defined in, the second amino acid from the N terminal being replaced by tyrosine, phenylalanine, methionine or tryptophan, and/or the amino acid at the C terminal being replaced by leucine, isoleucine or phenylalanine; and, Y 0 and Z 0 are mutually independently a peptide consisting of 0 to one amino acid or the entire Y 0 -X 0 -Z 0 consists of a partial peptide of the ASB4 protein represented by any one of SEQ ID Nos: 8, 20, 23 and 29.