Gastric adenosquamous carcinoma is known as an infrequent histological cancer with a poor prognosis. A 69-year-old man was revealed to have gastric squamous carcinoma on the gastric body remote from esophagus (cT4 cN3, cStage IV). A curative operation was impossible so he was treated with systemic chemotherapy using S-1+docetaxel. After 1 course, we changed to second-line chemotherapy combining CPT-11+CDDP because of heterochronic multiple hepatic metastases. PET-CT and CT findings after 5 courses of second-line therapy showed reduced primary tumor and metastatic lesions. The curative operation was performed based on the effective response with downstaging. The final histological diagnosis showed gastric adenosquamous carcinoma. The adjuvant chemotherapy of CPT-11 was continued without relapse for almost 2 years.