Trastuzumab is the first molecular-target medicine for gastric cancer in acknowledgment of the effectiveness and safety in a randomized controlled trial for the HER2-positive gastric cancer. The HER2-positive rate of gastric cancer tends to be high for a well-differentiated adenocarcinoma. We report a case of HER2-positive scirrhous gastric carcinoma we treated, for whom a complete response was obtained by trastuzumab combination therapy. He was a 62-year-old man. In April, 2006, he was diagnosed with metastatic scirrhous gastric carcinoma(mainly poorly-differentiated adenocarcinoma). We become clear with HER2 strong positive in a pathology tissue and started capecitabine+cisplatin+trastuzumab therapy. We confirmed the disappearance of the lesion at the 10th cycle and judged it to be a complete response. The HER2 of advanced gastric cancer must be screened immediately without asking patients for their background or their clinical and pathologic features.