Recently, the author experienced a case of rare myxofibroma, thought to be orignated from left maxillary sinus spreading to ethmoid and sphenoid sinuses. A 31-year-old man came to ENT OPD(NMC) with history of Co⁶⁰ therapy under suspicious myxofibroma. X-ray study revealed a large tumor infiltration in the left maxillary, ethmoid and sphenoid sinuses with bony destruction. We performed two times of surgical management combined with chemotherapy.