A 75-year-old woman was admitted to our department because of epigastric pain. Imagings revealed cancer of the head of the pancreas. She was an HBV carrier, although no liver dysfunction was observed. Her serum HBV-DNA level was lower than 2.6. We performed pancreaticoduodenectomy for pancreatic cancer. No postoperative complication was observed. The histopathological diagnosis was tubular adenocarcinoma of the pancreas. As a postoperative adjuvant chemotherapy, gemcitabine hydrochloride (GEM) was injected at a dose of 800mg/m2 once a week. Disorientation and jaundice were observed after six doses of GEM. Blood chemistry revealed that total bilirubin and ammonia were abnormally elevated, and that blood coagulant factors were diminished. Serum HBV-DNA level was lower than 2.6. It showed no reactivation of HBV. Abdominal CT showed no recurrence but fatty liver. Fresh frozen plasma was supplied and branched chain amino acids were injected after GEM was administration discontinued. Lactulose was also given orally. With these conservative treatments, she recovered completely. Careful monitoring of liver function during GEM administration is required in a HBV carrier.