A cross-linked peptide represented by the following chemical formula: (wherein, X is selected from the group consisting of the following chemical formulae: and wherein, n represents an integer of 1 to 12, m represents an integer of 1 to 24 and 1 represents an integer of 1 to 24.); Y is any one selected from the group consisting of the following compound Y1 and compound Y4: (wherein, o represents an integer of 1 to 12, p represents an integer of 1 to 27, q represents an integer of 1 to 24), Z represents hydrogen, an optionally substituted alkyl group having 1 to 30 carbon atoms, an optionally substituted acyl group having 1 to 36 carbon atoms, polyethylene glycol, a tBoc group, a Fmoc group, a Cbz group or a Nosyl group, represents a hydrogen atom, an optionally substituted acyl group having 1 to 6 carbon atoms or a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements, represents OH, an amino group or a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements, represents a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements (here, the sum of the numbers of amino acids of, and is at least 3), and and represent each independently a structure represented by any of the following formula: (wherein, R 1, R 3 and R 4 represent each independently a hydrogen atom or a methyl group, and R 2 represents a hydrogen atom or a side chain of an amino acid or unnatural amino acid.)). wherein, n represents an integer of 1 to 12, m represents an integer of 1 to 24 and 1 represents an integer of 1 to 24.); Y is any one selected from the group consisting of the following compound Y1 and compound Y4: (wherein, o represents an integer of 1 to 12, p represents an integer of 1 to 27, q represents an integer of 1 to 24), Z represents hydrogen, an optionally substituted alkyl group having 1 to 30 carbon atoms, an optionally substituted acyl group having 1 to 36 carbon atoms, polyethylene glycol, a tBoc group, a Fmoc group, a Cbz group or a Nosyl group, represents a hydrogen atom, an optionally substituted acyl group having 1 to 6 carbon atoms or a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements, represents OH, an amino group or a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements, represents a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements (here, the sum of the numbers of amino acids of, and is at least 3), and and represent each independently a structure represented by any of the following formula: (wherein, R 1, R 3 and R 4 represent each independently a hydrogen atom or a methyl group, and R 2 represents a hydrogen atom or a side chain of an amino acid or unnatural amino acid.)). (wherein, o represents an integer of 1 to 12, p represents an integer of 1 to 27, q represents an integer of 1 to 24), Z represents hydrogen, an optionally substituted alkyl group having 1 to 30 carbon atoms, an optionally substituted acyl group having 1 to 36 carbon atoms, polyethylene glycol, a tBoc group, a Fmoc group, a Cbz group or a Nosyl group, represents a hydrogen atom, an optionally substituted acyl group having 1 to 6 carbon atoms or a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements, represents OH, an amino group or a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements, represents a peptide having 1 to 20 residues composed of amino acids and/or unnatural amino acids as constituent elements (here, the sum of the numbers of amino acids of, and is at least 3), and and represent each independently a structure represented by any of the following formula: (wherein, R 1, R 3 and R 4 represent each independently a hydrogen atom or a methyl group, and R 2 represents a hydrogen atom or a side chain of an amino acid or unnatural amino acid.)).