Retroviral vector-producing cells for

gag-pol gene from a retrovirus, enhance the N- acetylglucosaminyltransferase III activity in cells carrying the env gene. By producing a retroviral vector using the cells, it is possible to obtain a retroviral vector that sugar chain structure is modified. Retroviral vectors prepared in accordance with the aforementioned method indicates a high infection efficiency, especially in the presence of a functional substance.