In neuro-Behcet's disease (NBD), myelitis is a rare clinical form. We report the case of a woman with NBD presenting with unsteady gait and generalized spasticity. Spinal magnetic resonance imaging (MRI) showed multiple and confluent hyperintensities extending throughout the entire spinal cord on a T2-weighted image with some contrast enhancement. High-dose steroid therapy was so effective that the myelitis was markedly improved, as shown in the follow-up MRI. Longitudinal myelitis involving the entire spinal cord, as seen in our patient, has never been described before. This case suggests that NBD could be one of the important differential diagnoses of longitudinal myelitis.