A 63-year-old man presented with a tumorous shadow in his right lower lung field by radiograph and was admitted to our hospital to determine if it was malignant. Computed tomography (CT) showed a solitary lesion (19 × 20 mm) in the right lower lobe. Fiberoptic bronchoscopy was performed. It demonstrated vegetation and some blistered material in the right lower lobe bronchus. The patient was diagnosed as having actinomycosis because histological examination of the biopsy specimen demonstrated actinomyces colonies and sulfur granules. The material was diagnosed as a squid's jaw plate. History revealed that he had sometimes eaten squid, which is a kind of snack food in Japan. The patient responded well to penicillin therapy, and chest X-ray and CT scan findings completely cleared the problem in six months. Physicians should keep in mind endobronchial actinomycosis caused by foreign bodies as one of the differential diagnoses of tumorous shadows on chest X-ray films and CT scans because it might affect patients who have a risk of aspiration.