Herein, a case of immunoglobulin G4 (IgG4)-related sclerosing cholangitis is reported. IgG4 was diagnosed based on observations from peroral cholangioscopy and laparoscopy, and these methods are proposed for definitive and precise diagnosis of this disease. A 76-year-old male patient with inguinal Paget's disease had intrahepatic bile duct dilatations detected with computed tomography at his periodic check-up. Magnetic resonance cholangiography showed stenosis of the upper common bile duct and poststenotic dilatation of left intrahepatic bile ducts. The portal tract and bilateral intrahepatic bile ducts were surrounded by a low-density area, facing a tumor-like lesion at segment 2. Cytological examinations of the stenotic and dilated lesions revealed no cellular atypia. Histological examination of the tumor showed normal liver tissue with infiltration of lymphocytes, indicating an inflammatory pseudotumor. Peroral cholangioscopy excluded the possibility of biliary cancer and indicated that the stenotic legion was of submucosal, not mucosal, origin. Laparoscopic observations showed discoloration with wide yellowish-white lobular markings and wide depressed lesions at segments 2 and 7. Liver histology showed mild cholangitis with infiltration of IgG4-positive plasma cells around the bile ducts. Serum IgG4 levels were elevated. From these findings, the patient was diagnosed with IgG4-related sclerosing cholangitis. After treatment with prednisolone, blood liver enzymes and IgG4 rapidly normalized, bile duct dilatations improved, and the hepatic pseudotumor disappeared. The cholangitis did not recur. In this case, biliary cancer was ruled out by observation with peroral cholangioscopy, and the spread of cholangitis in the liver periphery was verified with laparoscopy; this information could not be obtained with other modalities.