Abstract: The present invention relates to a method for mass-producing vaccinia virus using suspended cells. Although methods for producing vaccinia virus using adherent cells in the related art have limitations that are not suitable for mass production of viruses due to the characteristics of adherent cells, the present inventors have developed a technique capable of producing viruses even in a bioreactor using a low appropriate cell number, MOI, culture FBS concentration, and a medium while using suspended cells, and it was also confirmed that the present invention has high virus productivity similar to that in the case of using adherent cells. Accordingly, the technique of producing vaccinia virus using suspended cells according to the present invention enables mass production of vaccinia virus with high productivity.