The present invention relates to a method for the mass-production of exosome comprising a cargo protein, a vector for preparing the exosome, exosome including a cargo protein prepared by the method, and a method for loading the cargo protein to cytosol by using the exosome prepared thereby. According to the method for preparing an exosome comprising a cargo protein provided by the present invention, the exosome loaded with a cargo protein can be produced with a high yield, so that it can be used broadly in the treatment of disease using the exosome.