An oligonucleotide analogue useful for the antisense method, etc., having excellent enzyme resistance, having potent selective binding affinity for single-stranded RNA, and further having an excellent triplex-forming capacity with double-stranded DNA, and a nucleoside analogue useful for its production are provided.Nucleoside analogues, which are compounds of the general formula (I) and salts thereof, and oligonucleotide analogues containing one or more of the nucleoside analogues:where Base is an aromatic heterocyclic group or the like optionally having a substituent; R1, R2 and R3 are each a hydrogen atom, a protective group for an amino group, a protective group for a hydroxyl group, a phosphate group, or —P(R4)R5 [where R4 and R5 are each a hydroxyl group, a protected hydroxyl group, a mercapto group, a protected mercapto group, etc.]; m=0 to 2; and n=1 to 3].