Primary pulmonary artery sarcoma is very rare disease. The diagnosis of pulmonary artery sarcoma is frequently confused with pulmonary embolism because its clinical symptom and radiologic findings are similar with pulmonary embolism. It was often diagnosed at autopsy as it progresses rapidly. So Pulmonary artery sarcoma must be suspected if the origin of thrombus is not known and anticoagulation therapy is not effective. In this case, a 57 years old man who has been diagnosed pulmonary embolism was transferred to our department because of ineffective anticoagulant therapy and its worsening lesion despite of 5 month-therapy. In operative findings, it was pulmonary artery sarcoma that invaded to pericardium. There was angiosarcoma in right pulmonary artery, which metastasized to lung parenchyme. Under cardiopulmonary bypass, we resected main pulmonary artery and right lung. The Gore-tex graft was interposed between main pulmonary artery and left pulmonary artery. He was discharged after chemotherapy.