A 64-year-old woman was accidentally detected to have multiple cystic tumors measuring 30 mm in diameter in the pancreatic head in 2009. The probable diagnosis was a serous cystic neoplasm of the pancreas. However, the tumor had grown to 52 mm in diameter in 4 years, and endoscopic retrograde pancreatography (ERCP) showed stenosis of the main pancreatic duct. We performed subtotal stomach-preserving pancreaticoduodenectomy, and histopathological diagnosis was serous cystadenoma.