A case of a foreign body tumor resembling fungus ball pre-operatively diagnosed by bronchofiberscopic examination is reported. A 54-year-old male was referred with a complaint of fever. Chest X-ray and tomography showed a mass shadow with meniscus sign resembling fungus ball in the right lower lung field. Trans-bronchial lung biopsy revealed sulfur-granule of actinomycosis. In spite of local injection of sensitive antibiotics (ABPC) once a week for two months the mass shadow remained unchanged on X-ray. Bronchofiberscopic examination was performed again and a small piece of fibrous substance was obtained, which had been left in previous operation done 17 years before. Re-thoracotomy assured that the mass was a foreign body tumor caused by a gauze.