Intraductal papillary neoplasm of the bile duct (IPN-B) is a neoplastic lesion preceding invasive intrahepatic cholangiocarcinoma (ICC) and is a new definition of a tumor with papillary growth in the intra- or extra-hepatic bile duct. The authors reported a case of IPN-B with interesting histopathological findings and emphasized that cholangiography is especially helpful for the diagnosis of bile duct dilatation due to the infiltration of carcinoma cells.