A nucleoside derivative or a salt thereof, represented by the following chemical formula : where in the chemical formula , Su is an atomic group having a sugar skeleton at a nucleoside residue or an atomic group having a sugar phosphate skeleton at a nucleotide residue, L 1 and L 2 are each independently a straight-chain or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms, X 1 is an imino group (-NR 1 -), an ether group (-O-), or a thioether group (-S-), and R 1 is a hydrogen atom or a straight-chain or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms; wherein the atomic group having a sugar skeleton at a nucleoside residue or the atomic group having a sugar phosphate skeleton at a nucleotide residue is represented by the following chemical formula : where in the chemical formula , R 2 is a hydrogen atom, a protecting group, or a group represented by the following chemical formula , R 3 is a hydrogen atom, a protecting group, or a phosphoramidite group, R 4 is a hydrogen atom, a fluorine atom, a hydroxyl group, an amino group, or a mercapto group, where in the chemical formula , Y is an oxygen atom or a sulfur atom, Z is a hydroxyl group or an imidazole group, and m is an integer of 1 to 10. where in the chemical formula , Su is an atomic group having a sugar skeleton at a nucleoside residue or an atomic group having a sugar phosphate skeleton at a nucleotide residue, L 1 and L 2 are each independently a straight-chain or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms, X 1 is an imino group (-NR 1 -), an ether group (-O-), or a thioether group (-S-), and R 1 is a hydrogen atom or a straight-chain or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms; Su is an atomic group having a sugar skeleton at a nucleoside residue or an atomic group having a sugar phosphate skeleton at a nucleotide residue, L 1 and L 2 are each independently a straight-chain or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms, X 1 is an imino group (-NR 1 -), an ether group (-O-), or a thioether group (-S-), and R 1 is a hydrogen atom or a straight-chain or branched, saturated or unsaturated hydrocarbon group having 2 to 10 carbon atoms; wherein the atomic group having a sugar skeleton at a nucleoside residue or the atomic group having a sugar phosphate skeleton at a nucleotide residue is represented by the following chemical formula : where in the chemical formula , R 2 is a hydrogen atom, a protecting group, or a group represented by the following chemical formula , R 3 is a hydrogen atom, a protecting group, or a phosphoramidite group, R 4 is a hydrogen atom, a fluorine atom, a hydroxyl group, an amino group, or a mercapto group, R 2 is a hydrogen atom, a protecting group, or a group represented by the following chemical formula , R 3 is a hydrogen atom, a protecting group, or a phosphoramidite group, R 4 is a hydrogen atom, a fluorine atom, a hydroxyl group, an amino group, or a mercapto group, where in the chemical formula , Y is an oxygen atom or a sulfur atom, Z is a hydroxyl group or an imidazole group, and m is an integer of 1 to 10. Y is an oxygen atom or a sulfur atom, Z is a hydroxyl group or an imidazole group, and m is an integer of 1 to 10. <EOS>