Primary cardiac tumors are extremely rare and about 20-25% of primary cardiac tumors are malignant. Recently we have experienced a case of primary cardiac rhabdomyosarcoma originated on the right atrial wall. Patient was 41 years-old women and chief complaints were pitting edema and exertional dyspnea. Emergency operation was performed to relieve symptoms by pericardial effusion that hac been seen on the echocardiogram and large soft mass in right atrial cavity on the MRI. About 700ml amounts of bloody pericardial effusion was collected into the pericardial cavity. 4X5X5 cm sized ingrowing soft mass in the right atrial cavity and two small sized outgrowing masses were inspected. A tumor was invaded into the SA node and superior limbic portion of fossa ovalis. And then mass & right atrial free wall was resected but areas of SA node and fossa ovalis were not resected. Defect of right atrial wall was reconstruced with bovine patch. She was discharged after 2 weeks without any problems and she has been treated with chemotherapy.