Provided are: a method for suppressing the particulation and/or secretion of HBV in infected hepatocytes； a method for treating or suppressing HBV infection thereby； and a medicinal composition therefor. The present invention is characterized in that an inhibitor of the expression of at least one sugar chain gene selected from among SLC35B1 gene, CHST9 gene and ST8SIA3 gene, or an inhibitor of sugar chain modification activity of at least one sugar chain synthesis-related protein selected from among SLC35B1, CHST9 and ST8SIA3 is used as a suppressor of HBV secretion from HBV-infected hepatocytes or an inhibitor of HBV particulation. The aforesaid suppressor of sugar chain gene expression or inhibitor of sugar chain modification activity of a sugar chain synthesis-related protein can be used, either alone or in combination, as a medicinal composition for preventing and treating HBV infection.
