The present invention relates to a cell line having an increased ability to produce virus and a method for preparing thereof, and more particularly, to a cell line that has an increased ability to produce virus, due to the loss of the function of the Bst-2 (tetherin) gene, and to a production method thereof. According to the present invention, a cell line lacking the function of the Bst-2 gene has an excellent ability to produce virus, compared to a wild-type cell line. Thus, when the mutant cell line is used as a virus-producing cell line, the production yield of virus can be increased. In addition, the mutant cell line can be used for the production and research of vaccines for preventing and treating viral diseases.