A 66-year-old man presented with headache and ophthalmalgia. Diplopia developed, and he was hospitalized. The left eye had abducent paralysis and proptosis. We diagnosed him with Tolosa-Hunt syndrome and administered methylprednisolone at 1 g/day for 3 days. However, the patient did not respond to treatment. No abnormality was found on his MRI or cerebrospinal fluid examination. Tests showed his serum immunoglobulin G4 and antineutrophil cytoplasmic antibody titers were within normal limits. He also had untreated diabetes mellitus (HbA1c 9.2). One week after first presenting with symptoms, herpes zoster appeared on the patient\'s dorsum nasi, followed by keratitis and a corneal ulcer. Herpes zoster ophthalmicus with ophthalmoplegia was diagnosed. We began treatment with acyclovir (15 mg/kg) and prednisolone (1 mg/kg, decreased gradually). Ophthalmalgia and the eruption improved immediately. The eye movement disorder improved gradually over several months. It is rare that diplopia appears prior to cingulate eruption of herpes zoster ophthalmicus. We speculated that onset of the eruption was inhibited by strong steroid therapy and untreated diabetes mellitus.