As means for solving the problem of providing a nucleic acid conjugate that does not undergo degradation at a DNA-RNA bonding site even in vivo, provided is a nucleic acid conjugate comprising a single-stranded DNA and a double-stranded RNA, wherein the 3' position of the 3'-terminal deoxyribonucleotide residue of the single-stranded DNA is bound to the 5' position of the 5'-terminal ribonucleotide residue of one of the ribonucleotide strands of the double-stranded RNA, and the hydroxyl group at the 2' position of the 5'-terminal nucleotide of the ribonucleotide strand, which is bound to the single-stranded DNA, is substituted with an alkoxy group or a halogen atom, and/or the phosphate diester group between the 3' position of the first ribonucleotide bound to the single-stranded DNA and the 5' position of the adjacent ribonucleotide is substituted with any of phosphorothioate group, dithiophosphate diester group and trithiophosphate diester group.
