Pulmonary aneurysm is a rare vascular anomaly.Infection is one of major causes of pulmonary aneurysms. Pulmonary aneurysm by pulmonary actinomycosis is a rare case. Our case is maybe the first case in Korea,so far similar case has not been reported Worldwide written in English. We describe a 73-year-old man with aneurysm of pulmonary artery caused by actinomycosis infection on lung. We detected aneurysm by angiography of pulmonary artery, and actinomycosis infection was revealed by confirm sulfur granules on specimens taken by percutaneous needle aspiration(PCNA). Antibiotic therapy was applied to this patient and aneurym was embolized with coils.With this therapy,the patient was successfully managed and improved.