A 80-year-old man was referred to our hospital complained of tarry stool and appetite loss. Upper GI endoscopy revealed III+IIc like lesion (adenocarcinoma) in cardia and submucosal elevated lesion in prepyrolic region and type 2 lesion (small cell carcinoma) in the duodenal bulbus. Because of his herniplesia after cerebral hemorrhage, his activity of daily life was low and he and his family chose chemotherapy rather than operation. He received S-1 combined with CDDP therapy (80 mg of TS-1 administered for 14 days followed by 14 days rest+ 10 mg/day of CDDP was administered from day 8 for 5 days). After 2 courses of chemotherapy, both lesion was dramatically improved. Small cell carcinoma of the duodenum is very rare and known to be aggressive with early dissemination and metastasis, early diagnosis and treatment including chemotherapy should be considered.