A peptide composed of an amino acid sequence represented by general formula shown below: [Formula 1] X 11 -(Y 11 -X 12) 11 wherein in general formula, X 11 is a peptide residue composed of an amino acid sequence of (a) or (b) below: (a) an amino acid sequence represented by any of SEQ ID NOs: 1 and 12-14, (b) an amino acid sequence including substitution of the arginine first from the N-terminus with glycine, alanine, lysine, serine, threonine or histidine, substitution of the lysine second from the C-terminus with glycine, alanine, arginine, histidine, serine or threonine, and substitution of the proline first from the C-terminus with glycine, alanine, serine, threonine, valine, leucine or isoleucine in an amino acid sequence represented by any of SEQ ID NO: 1; Y 11 is a peptide linker composed of an amino acid residue of at least 1 but not more than 3 amino acids, wherein each amino acid residue is independently a glycine residue, a serine residue, a cysteine residue or a lysine residue; X 12 is either a peptide residue composed of an amino acid sequence of (a) or (b) above, or a retro-inverso peptide residue thereof; and n11 represents an integer of at least 1 but not more than 3; wherein, optionally, the peptide is absorbed and accumulates in cancer cells or cancer tissue in a digestive system to a high degree compared with the accumulation observed in normal tissue and malignant tumor cells within other systems. wherein in general formula, X 11 is a peptide residue composed of an amino acid sequence of (a) or (b) below: (a) an amino acid sequence represented by any of SEQ ID NOs: 1 and 12-14, (b) an amino acid sequence including substitution of the arginine first from the N-terminus with glycine, alanine, lysine, serine, threonine or histidine, substitution of the lysine second from the C-terminus with glycine, alanine, arginine, histidine, serine or threonine, and substitution of the proline first from the C-terminus with glycine, alanine, serine, threonine, valine, leucine or isoleucine in an amino acid sequence represented by any of SEQ ID NO: 1; Y 11 is a peptide linker composed of an amino acid residue of at least 1 but not more than 3 amino acids, wherein each amino acid residue is independently a glycine residue, a serine residue, a cysteine residue or a lysine residue; X 12 is either a peptide residue composed of an amino acid sequence of (a) or (b) above, or a retro-inverso peptide residue thereof; and n11 represents an integer of at least 1 but not more than 3; (a) an amino acid sequence represented by any of SEQ ID NOs: 1 and 12-14, (b) an amino acid sequence including substitution of the arginine first from the N-terminus with glycine, alanine, lysine, serine, threonine or histidine, substitution of the lysine second from the C-terminus with glycine, alanine, arginine, histidine, serine or threonine, and substitution of the proline first from the C-terminus with glycine, alanine, serine, threonine, valine, leucine or isoleucine in an amino acid sequence represented by any of SEQ ID NO: 1; Y 11 is a peptide linker composed of an amino acid residue of at least 1 but not more than 3 amino acids, wherein each amino acid residue is independently a glycine residue, a serine residue, a cysteine residue or a lysine residue; X 12 is either a peptide residue composed of an amino acid sequence of (a) or (b) above, or a retro-inverso peptide residue thereof; and n11 represents an integer of at least 1 but not more than 3; Y 11 is a peptide linker composed of an amino acid residue of at least 1 but not more than 3 amino acids, wherein each amino acid residue is independently a glycine residue, a serine residue, a cysteine residue or a lysine residue; X 12 is either a peptide residue composed of an amino acid sequence of (a) or (b) above, or a retro-inverso peptide residue thereof; and n11 represents an integer of at least 1 but not more than 3; wherein, optionally, the peptide is absorbed and accumulates in cancer cells or cancer tissue in a digestive system to a high degree compared with the accumulation observed in normal tissue and malignant tumor cells within other systems.