A 79-year-old man complaining of epigastralgia was examined and diagnosed with advanced gastric cancer (UML, Type 5, Ant-Less-Gre, cT4a, cN1, cH0, cP1, cStage IV). A poor prognosis was predicted, but we tried preoperative chemotherapy hoping for a down-staging of the tumor. We chose a regimen of S-1 plus cisplatin as follows: S-1 (60 mg/m2) was administered orally for 3 weeks followed 2 weeks of rest, and cisplatin (50 mg/m2) was administered by intravenous drip on day 8. After three cycles of treatment, diagnostic laparoscopic examination revealed a suspected serosal invasion of the main tumor, but peritoneal dissemination was not seen, and abdominal washing cytology was negative. After the fourth cycle of treatment, total gastrectomy with lymph node dissection (D1+No. 7, 8a, 9, R0) was performed. Histological examination of the resected specimens revealed no residual cancer cells in the primary lesion or regional lymph nodes, resulting in a diagnosis of complete response to chemotherapy according to the Japanese Classification of Gastric Carcinoma. The postoperative course was uneventful, and he has been fine as an outpatient.