The author observed a 35-year-old male patient who came to the Dental Infirmary of Kyungpook National University Hospital who had complained of gradual swelling on both side of the mandible for 15 years. As a result of careful analysis of clinical, radiological and histopathological findings, the authors diagnosed it as cementifying fibroma and obtained the results as follows: 1. In clinical examination, main clinical symptom was facial deformity due to gradual swelling on both side of the mandible. 2. In radiographic examination, radiolucent lesions with central radiopaque foci were seen on both mandibular body areas bilaterally, and cortical thinning and expansion of the mandibular body were seen buccolingually. And loss of lamina dura and root resortption of adjacent teeth were also seen. In histopathological examination, this lesion was composed of delicate interlacing collagen fibers interspersed by the fibroblasts and cementoblasts. And round or oval shaped basophilic masses of cementum-like tissue were observed in the connective tissue.