Ewing's sarcoma is an uncommon malignancy primarily affecting bone tissue and usually occurs in adolescents and young adults. This paper reports a rare case of extra-skeletal Ewing’s sarcoma of the oral cavity soft tissue. In the clinical examination, a mass of 1.5×1.5 cm in diameter was observed in the right mandibular vestibule. Radiographic examination revealed no involvement of mandible. Microscopically, the tumor was composed of malignant small round cell tumor that exhibited immunoreactivity for CD99. The patient was subjected to enucleation surgery under local anesthesia, prognosis was excellent, and the patient remained symptom-free after 13 months.