We report a case of superficial bile duct carcinoma showing extensive intraductal spread without dilatation of the bile duct in which diagnosis was established preoperatively by transpapillary forceps biopsy and intraductal ultrasonography. A 78-year-old man was given a diagnosis of acute cholecystitis, and percutaneous transhepatic gallbladder drainage (PTGBD) was performed. Cholangiography via the PTGBD tube revealed a tiny irregularity in the hilar bile duct. Transpapillary intraductal ultrasonography showed that this irregularity extended from the intrahepatic bile duct to the middle of the bile duct. Bile duct biopsy revealed malignancy, and thus bile duct resection and hepaticojejunostomy were performed. Histological examination verified a well-differentiated adenocarcinoma confined to the epithelium and the fibromuscular layer.