A 66-year-old man was referred to our hospital because of cough. Chest X-ray films showed complete atelectasis of the left lung. Serum CYFRA was elevated. Bronchoscopic examination disclosed a white polypoid lesion occluding the left main bronchus. A biopsy specimen from the lesion revealed numerous aspergillus hyphae. Oral itraconazole (100 mg) and weekly endobronchial instillation of fluconazole were administered. Three months later, on the 12th bronchoscopic examination, the tumor occluding the left main bronchus was detected after the removal of aspergillus, and the biopsy findings yielded a diagnosis of squamous cell carcinoma. Aspergillosis complicated by lung cancer without cavity formation is very rare, and compounded the difficulty of diagnosing lung cancer in this case.