The present invention relates to a pharmaceutical composition for treating cerebrovascular diseases, containing a stem cell-derived exosome as an active ingredient. The stem cell-derived exosome according to the present invention has remarkable nerve cell protective effects such as the inhibition of ventricular enlargement in the intraventricular hemorrhage (IVH) animal model, the decrease in hydrocephalus, and the inhibition of nerve cell death and inflammatory cells, and thus can be useful for treating cerebrovascular diseases including IVH and the like.