A 63-year-old woman with appetite loss and general fatigue underwent gastrointestinal fiberscopy, which revealed type 2 advanced gastric cancer. Multidetector-row computed tomography revealed a massive gastric cancer invading the left hepatic lobe, pancreatic head, and common hepatic artery, as well as revealing a duplicated hepatic artery in which the right hepatic artery branched directly from the celiac axis, and ran behind the splenic vein. On the other hand, the common hepatic artery ran anterior to the splenic vein. We were able to perform pancreaticoduodenectomy with common hepatic artery resection and left lobectomy as curative surgery because her duplicated hepatic artery enabled us to ligate the common hepatic artery. Her postoperative clinical course was uneventful, and she is in good health 3 years after the surgery, without recurrence. We consider that multidetector-row computed tomography is very useful for the diagnosis of vascular anomaly, preoperative staging and decision making on the appropriate surgical strategy.