A 63-year-old man was found to have an upper abdominal mass, and was referred to our hospital. Endoscopic examination and abdominal CT showed gastric cancer with liver metastasis. A large metastatic tumor of the liver invaded the hepatic hilus, making curative resection impossible. We started chemotherapy using S-1(120 mg/body/day), orally administered for three weeks followed by 2-week rest period, and cisplatin(100mg/body), administered intravenously on day 8 as 1 course. After 5 courses of chemotherapy, the liver tumor reduced markedly and the gastric cancer pathologically disappeared, enabling partial gastrectomy and left hepatectomy. Histological examination showed a well-differentiated adenocarcinoma in the mucosal layer of the resected stomach. A resected specimen of the liver showed a moderately-differentiated adenocarcinoma with signet-ring cells, compatible to liver metastasis from gastric cancer. Bile leakage the remaining liver occurred, but he recovered soon. Gastrointestinal examination revealed another early gastric cancer after seeing him for 2 years on an outpatient basis. We conducted subtotal gastrectomy, and the patient remains alive 30 months after the first operation. This case suggests that S-1/CDDP chemotherapy may reduce the stage of unresectable liver metastasis from gastric cancer and make a curative operation possible.