A nucleoside that is more practical for RNA pharmaceuticals and other applications and use thereof is represented by formula (1) or (2) below, or a salt thereof:




(In formula (1), R1 represents a hydrogen atom, a hydroxyl group, a hydroxyl group in which a hydrogen atom is substituted by an alkyl group or alkenyl group, or a protected group, and in formula (2), X represents a halogen atom. In formula (1) and formula (2), R2 and R3 may be the same or different, and each represents a hydrogen atom etc., R4 represents NHR7 (in which R7 represents a hydrogen atom etc., and B represent represents any of a purine-9-yl group, 2-oxo-pyrimidin-1-yl group, substituted purine-9-yl group or substituted 2-oxo-pyrimidin-1-yl group).