Extrapulmonary small cell carcinoma originated from the paranasal sinus is extremely rare, and its local and distant metastasis is common and the prognosis is poor. We recently experienced a rare case of small cell carcinoma that originated from the maxillary sinus. However, the diagnosis was delayed for several reasons, one of which included accompanied bilateral fungal sinusitis. The patient received chemotherapy for four times, but the therapy was discontinued due to poor general conditions. We report our case with a review of the literature.