Primary pulmonary artery sarcoma is a rare tumor and commonly misdiagnosed as pulmonary embolism. The prognosis of these tumors is very poor. The Median length of survival without surgical resection is approximately 1.5 months, but surgical resection has lengthened survival time to approximately 1 year. We encountered a case of primary pulmonary artery sarcoma, with a 55 year-old woman whose symptoms were exertional dysp ea, right chest pain, and hemoptysis. A preoperative chest CT scan revealed mass lesion mimicking pulmonary embolism. Pulmonary angioplasty and right Pneumonectomy were Performed on partial cardiopulmonary bypass. Postoperatively the mass was confirmed as undifferenciated sarcoma histopathologically. The symptoms were somewhat improved, but the patient died of unknown causes about 3 months after surgery.