PROBLEM TO BE SOLVED: To provide an anti-influenza agent having a high binding constant to an influenza virus without any influence of virus mutation.SOLUTION: The glycosylated nucleic acid, wherein a nucleic acid is bound to a sugar through a linker, includes a sialic acid as the sugar. Using the glycosylated nucleic acid including the sialic acid as a sugar, molecular designing can be carried out relatively easily with consideration given to the structure of the sugar chain binding site of HA (haemagglutinin) of the influenza virus. Since an amino acid residue mutation hardly occur in the region bound to the sialic acid of the HA of the influenza virus, the anti-influenza agent having a high binding constant can be provided without being affected by virus mutation.
