The present invention relates to the use of carbon nanotubes for preventing or treating brain disease, and more particularly, to a composition for protecting cranial nerves, to a composition for preventing or treating neurodegenerative diseases or ischemic brain disease or to a composition for treating traumatic injuries to the central nervous system, containing carbon nanotubes as an active ingredient, to the use of carbon nanotubes for preparing a therapeutic agent for the abovementioned diseases and to a method for treating the abovementioned diseases. The composition of the present invention enables patients to recover from physical damage to the brain, exhibits superior efficacy for inhibiting the onset of Parkinson's disease and strokes in animal models for Parkinson's disease and strokes, and the cytotoxic effects of beta amyloid in beta amyloid toxicity tests. Therefore, the composition of the present invention can be effectively used in the preparation of medicine for protecting cranial nerves, therapeutic agents for preventing or treating brain disease, or therapeutic agents for treating traumatic injuries to the central nervous system.