Primary pulmonary arterial sarcomas, especially those originating from the pulmonary valve are extremely rare. A 35 year-old male patient was admitted for exertional dyspnea and fatigue. Large intraluminal mass in the main pulmonary artery and both pulmonary arteries was detected by chest computed tomogram, chest magnetic resonance imaging, echocardiogram, and pulmonary angiogram. We regarded the mass as a primary pulmonary arterial malignant tumor, and resected under cardiopulmonary bypass. The mass was appeared to originate from the posterior cusp of pulmonary valve, and extended from below pulmonary valve to main pulmonary artery and both pulmonary arteries. We resected the mass by pulmonary endarterectomy and replaced the pulmonary valve. The mass was diagnosed as a pulmonary arterial sarcoma in histopathologic examination.