A 53 year old man with gastric cancer was admitted for radical subtotal gastrectomy. The patient received general anesthesia with epidural analgesia. Epidural catheterization was performed using an 18-gauge Tuohy needle at the T10-11 interspace, and the epidural space was confirmed after a repeated attempt. An epidural catheter was then advanced smoothly 5 cm in cephalad direction without bleeding or CSF leakage. The patient received a test dose of lidocaine and epinephrine and continuous infusion with morphine and lidocaine 30 minutes before operation finished. Vital signs during the operation were stable. Two days after the operation, the patient complained of an orthostatic headache, and relieved ketolorac. On the seventh day, the patient complained of bilateral diplopia. Diffuse pachymeningeal gadolonium enhancement was seen on the brain MRI, and his CSF pressure was 0 mmHg by spinal tapping. We suspected abducent nerve palsy due to CSF hypovolemia and performed an epidural blood patch with 15 ml of autologus blood at the previous puncture site. The patient is receiving regular examinations at the Neurology and Opthalmology department. Abducent nerve palsy completely recovered by the Hess Screen test 6 months after operation, and diplopia disappeared 10 months after the operation.