A 64-year-old female presented with a left cervical tumor. Gastrointestinal endoscopic examination showed advanced gastric cancer type 3, which was diagnosed as poorly-differentiated adenocarcinoma. Computed tomography (CT) showed hugely enlarged Virchow and para-aortic lymph nodes. She was treated with oral S-1, 100 mg/day for 28 days, followed by a 2-week rest. After two courses, S-1 was administered for 14 days followed by a 7-day rest because of side effects. After five courses of treatment, CT showed complete disappearance of the lymph node metastases. Total gastrectomy and lymph node dissection were performed. The histology was judged as Grade 2. The residual cancer in the stomach was only 2mm in size, and there were no viable cancer cells in any lymph nodes. One year postoperatively, the patient is alive without recurrence.