An 80-year-old woman was admitted to our hospital with complaints of jaundice and liver dysfunction. She was found to have a high titer of serum IgG4, positive rheumatoid factor and marked elevation of DUPAN-2 (11,148 U/ml). Computed tomography showed swelling of the pancreas, and endoscopic retrograde cholangiopancreatography revealed diffuse irregular narrowing of the main pancreatic duct, which are typical findings of autoimmune pancreatitis. There was no evidence of malignancy. Administration of 30 mg/day of prednisolone was started. Computed tomography showed significant regression in the size of the pancreas, and the stenosis of the main pancreatic duct was improved on ERCP. The serum level of DUPAN-2 was also markedly decreased after the treatment.