A 16-year-old female was admitted to Wonkwang dental hospital with a chief complaint of painful ulceration on right buccal mucosa around mandibular 3rd molar area. Computed tomography and magnetic resonance imaging showed relative large soft tissue mass on the infratemporal fossa and masseter muscle region. By the feature of T1-weighted and T2-weighted of MR imaging, we suspected this mass as a kind of myogenic sarcoma. Histopathological and immunohistochemical studies established a definitive diagnosis of embryonal rhabdomyosarcoma. A review of the literature was also presented.