Because of the rarity of primary duodenal cancer, the coexistence of this disease with gastric cancer is very rare. The case presented herein suffered from two carcinomas of the duodenum and six gastric cancers. The patient was 71-year-old man who underwent subtotal gastrectomy and pancreatoduodenectomy. Pathologic studies showed that all of the gastric and one of the duodenal cancers were limited to the mucosal layer and that the other duodenal tumor invaded to the pancreas. Several cases of double cancers in the duodenum and the stomach have been reported in Japan, and this is first of multiple carcinomas of the duodenum associated with multiple gastric cancers.