The purpose of the present invention is to develop a system for efficiently constituting cyanoethyl ethers under mild conditions and probability of the ethers as functional groups for imparting specific functions and to make a contribution to the production of novel functional nucleic acids. The present invention relates to a nucleoside that is represented by the general formula (I) or a nucleotide derived therefrom: wherein X and Y may be the same as or different from each other, and are hydrogen, optionally substituted silyl group, 4-methoxytrityl group, 4,4'-dimethoxytrityl group or a group represented by the general formula (II): wherein R1 and R2 may be the same as or different from each other, representing an alkyl group having 1-7 carbon atoms such as diisopropyl, or they are united with each other to form a ring structure, R3 represents a protective group for a phosphoric acid such as 2-cyanoethyl; and B1 represents an optionally substituted pyrimidine or purine base.