A 54-year-old female presented with a very rare intraosseous neurofibroma of the frontal bone manifesting as forehead bulging. Skull radiography showed a radiolucent round lesion. Magnetic resonance imaging showed a mass lesion expanding from the frontal bone diploic layer to the epidural space. Fluorodeoxyglucose positron emission tomography and thallium-201 single photon emission computed tomography findings indicated tumor malignancy. The tumor was resected, and the histological diagnosis was benign intraosseous neurofibroma. Intraosseous neurofibroma usually occurs in the mandible. The origin of the present case may have been a peripheral nerve in the diploic vascular tissue.