Abstract: The present invention relates to a composition for an immunopotentiator (adjuvant) containing poly-gamma-glutamic acid and a composition for a vaccine containing the immunopotentiator, and more particularly, to an immunopotentiator containing poly-gamma-glutamic acid capable of enhancing antibody production rate by administering it to an animal together with antigen having low immunogenicity, and a composition for a vaccine containing the immunopotentiator and antigen. The inventive adjuvant has almost no toxicity and side effects, and show high antibody titer even when it is used with antigen having poor immunogenicity, so it can be used by adding to medical composition including preventive or curative vaccine for non-contagious chronic diseases as well as cancer, especially prostatic carcinoma, colon carcinoma, lung cancer, breast cancer, ovarian cancer, head and neck cancer, pudendum cancer, bladder cancer, brain tumor and glioma.