Salivary duct carcinoma histologically resembles an invasive mammary ductal carcinoma and is a malignant tumor with a poor prognosis. The rarity of this carcinoma has resulted in a lack of consensus on its chemotherapy regimen. In recent years, HER2 overexpression has been reported in not only breast cancer but also salivary duct carcinoma, so we performed an immunostaining on the surgical specimens of salivary duct carcinoma and analyzed the relationship between HER2 expression and the clinical background. As a result, 3 cases were found to be HER2-positive. In salivary gland carcinomas, the HER2 positive rate was 60% in salivary duct carcinomas, 0% in adenoid cystic carcinomas, 17% in mucoepidermoid carcinomas, 38% in adenocarcinomas. For the examination of pathological grade in salivary duct carcinoma, all HER2-positive patients belonged in a pathological high-grade group, whereas all HER2-negative cases belonged in a low-grade group. This result suggests a relation between HER2 expression and pathological grade. It is hoped that a new treatment strategy using the anti-HER2 antibody will be developed for HER2-positive salivary duct carcinoma.