The WHO separates odontogenic carcinomas into three groups : malignant ameloblastoma, primary intraosseous carcinoma(PIOC), and carcinomas arising from odontogenic epithelium including those arising from odontogenic cysts. In WHO criteria, primary intraosseous carcinoma is defined as a squamous cell carcinoma arising within the jaw, having no connection with the oral mucosa, and no developing from residues of odontogenic epithelium. This is a case of 52-year old man who had prolonged jaw pain and final diagnosis was primary intraosseous carcinoma(PIOC) on mandible. We obtained successful result after composite resection combined with hemimandibulectomy, RND, following reconstruction with latissmus dorsi myocutaneous flap, and postoperative radiation therapy.