Spontaneous hematomyelia (intramedullary spinal hematoma) is an uncommon event of an unknown cause. A 35-year-old man experienced sudden paresthesia over the chest, radiating pain, and motor weakness followed by complete paraplegia appeared after 1 hour. The preoperative diagnosis was made by magnetic resonance imaging which revealed hemorrhages from T4 to T9 cord segments. The selective spinal angiography, CSF study, blood laboratory, and pathology revealed no apparent cause for the hemorrhages.