Recently, osteonecrosis of the jaw (ONJ) with bisphosphonates is frequently reported. ONJ due to bisphosphonate is an adverse event in the treatment of breast cancer with bone metastasis. We report a case of ONJ due to bisphosphonates. A 66-year-old woman was admitted to our hospital due to right advanced breast cancer with bone metastasis. She received neo-adjuvant chemotherapy consisting of paclitaxel 70 mg/m2, qw, trastuzumab 2 mg/m2, qw. After chemotherapy, we performed modified mastectomy for local control. Postoperative adjuvant chemotherapy was added with bisphosphonate for bone metastasis of breast cancer. After bisphosphonate was used 14 times, she had a pain and pus-discharge in her lower jaw. The dentists' diagnosis was ONJ. We treated her with antibiotics and local minor curettage. The inflammatory symptoms almost disappeared. In this case, the administration of bisphosphonates was thought to be a major risk factor for ONJ. We think that special precautions for ONJ should be taken in patients administered bisphosphonates for bone metastasis of breast cancer.