A 27-year-old woman was diagnosed with gastric cancer complicated peritoneal dissemination and direct invasion to pancreas via staging laparoscopy. After systemic chemotherapy using regimen of S-1/CDDP for 2courses, the tumor did not increase in size and peritoneal dissemination did not progress. The patient subsequently underwent distal gastrectomy as a curative surgery. The histological diagnosis was ypT4bN1M0, ypStage III B. The patient was treated with DOC/CDDP for 6 courses after surgery as adjuvant therapy. At present 6 years after surgery, the patient is alive without tumor recurrence.