By introducing hepatocyte growth factor (HGF) gene and/or vascular endothelial growth factor (VEGF) gene into the subarachnoid space in humans, cerebrovascular disorders such as cerebrovascular obstruction, cerebral infarction, cerebral thrombosis, cerebral embolism, stroke, cerebral bleeding, moyamoya disease, cerebrovascular dementia, and Alzheimer's dementia can be effectively treated or prevented.