A 56-year-old woman diagnosed with type 2 gastric cancer and multiple lymph node metastases(T3N3M1[lym], cStage Ⅳ)was treated with chemotherapy using trastuzumab with S-1 plus cisplatin for 6 cycles. The primary lesion showed PR, and lymph node metastases disappeared after the chemotherapy. Because of adverse events, she was administered with 2 additional cycles of trastuzumab with S-1 plus cisplatin and 6 cycles of trastuzumab with capecitabine plus oxaliplatin. However, the primary lesion increased in size. Therefore, she underwent distal gastrectomy and D1+ lymphadenectomy with para-aortic lymph node sampling as a conversion surgery. The pathological diagnosis was T2N0M0, pStage ⅠB, and the primary cancer was Grade 1a owing to the chemotherapeutic effect. She survives without recurrence or postoperative adjuvant therapies 3 years after the surgery.