The term odontoma, first introduced by Broca, was originally applied to all odontogenic tumors. Related to the clinical and histological differences, 2 groups of odontoma were defined: compound odontoma and complex odontoma. Complex odontoma is more common in the mandible than in the maxilla, usually occuring in the mandibular premolar-molar area. And this consists of small mass of irregularly arranged enamel, dentine, cementum, and connective tissue, but tooth-like structures are not found. In our case, 34 year old man was diagnosed as the complex odontoma of maxillary sinus by the physical exam, Panex, and C.T scan. We sectioned and removed it, and then confirmed the diagnosis histopathologically. Its uncommon location and size made us report that case and review the literature concerned.