Provided is an antisense oligonucleotide having reduced toxicity. This antisense oligonucleotide has a central region, a 5'-side region, and a 3'-side region, and is characterized by having, in the central region: a nucleotide in which the 2'-position and 3'-position of the sugar moiety thereof are cross-linked (2'-3' cross-linked nucleotide); and/or a non-cross-linked nucleotide having a substituent at position 3' thereof (position 3'-modified non-cross-linked nucleotide).