The present invention relates to a composition for treating inflammatory brain diseases, which includes stem cell-derived exosomes as an active ingredient. The stem cell-derived exosomes according to the present invention can be usefully applied to the treatment of inflammatory brain diseases, because the exosomes have outstanding therapeutic effects, including inhibiting cell death due to inflammation in nerve cells, increasing the survival rate in an inflammatory-brain-disease animal model, and substantially reducing brain damage and inflammatory cytokine levels due to inflammatory reactions such as edema.
