We describe a case of Sjögren syndrome presenting with subacute transverse myelopathy that improved in response to steroid therapy. A 55-year-old woman with a history of NIDDM developed progressive sensory disturbance and weakness of the both legs, and micturition disturbance during a 6-month period, resulting in walking difficulty. On admission, neurological examination revealed paraplegia with extensor plantar reflex and sensory disturbance below Th 6 level. Lumbar puncture disclosed a normal cell count and a mild elevation of protein in the CSF. As subacute myelitis at the level of Th 6 was suspected, spinal plain and enhanced MRI was performed, which revealed no abnormalities. In contrast, tibial somatosensory evoked potential (SEP) could not be evoked while median SEP was almost normal, indicating thoracic cord involvement. She was diagnosed with primary Sjögren syndrome based on xerostomia, apple-tree appearance in parotid sialography, mononuclear cell infiltration in the salivary gland biopsied, and elevated anti-SS-A and SS-B antibody titers. We considered that her myelopathy was associated with Sjögren syndrome, and started steroid pulse therapy. After three courses of steroid pulse therapy followed by oral prednisolone, she showed clinical and SEP improvements. It is conceivable that the present case may represent Sjögren syndrome complicated with myelopathy that shows no MRI abnormality and well responds to steroid therapy. SEP can be a valuable tool for assessing the presence and severity of spinal cord involvement, and the efficacy of treatments.