In March 2011, trastuzumab was approved for treating human epidermal growth factor receptor 2 (HER2) positive advanced gastric cancer (AGC) in Japan. Therefore, all patients with AGC should be evaluated for HER2 status. In this study, we analyzed the clinicopathological features and current status of treatment in HER2 positive gastric cancer. One hundred 6 gastric cancer patients were examined for HER2 expression in our hospital between March 2011 and August 2014. Sixteen patients (15.1%) were HER2 positive. There was no correlation between HER2 status and age, sex, and location of tumor; however, HER2 positivity was significantly more frequent in patients with intestinal type tumors and had a tendency towards being more frequent in patients with macroscopic types 0, 1 or 2. Trastuzumab was administered to 10 patients with HER2 positive AGC. The total number of doses of trastuzumab was 1 to 44 (median 7.5), and the therapeutic effect of trastuzumab combination chemotherapy was 1 patient with a complete response and 4 with a partial response. Adverse events due to trastuzumab were not observed. The incidence of HER2 over-expression was 15.1%, and trastuzumab combination chemotherapy was relatively safe and effective.