Double-stranded oligonucleotides useful as decoy oligonucleotides having a high binding ability to a transcription factor and having a reduced cytotoxicity are disclosed. Each of the double-stranded oligonucleotides is formed by hybridization of a sense strand oligonucleotide of the following Formula A: 5 ² - N m - G - Consensus Sequence - C - N n - 3 ² (wherein N(m) is a flanking sequence at the 5'-end, and represents that "N"(s) in the number of m is(are) ligated; N(n) is a flanking sequence at the 3'-end, and represents that "N"(s) in the number of m is(are) ligated; all "N"(s) each independently represent(s) nucleotide A, G, T, C or U; m and n represent each independently an integer of 0 to 20; and Consensus Sequence represents a consensus sequence to which a transcription factor binds) and an antisense strand oligonucleotide complementary to said sense strand oligonucleotide.