An 80-year-old woman who had been suffering from atrial fibrillation and recurrent cerebral infarction was admitted to our hospital. Transesophageal echocardiography revealed a giant mobile thrombus in the left atrial appendage. The patient underwent thrombectomy and left atrial appendage obliteration under cardiopulmonary bypass. Her postoperative course was uneventful. The patient showed no recurrence of the left atrial thrombus nor thromboenbolism postoperatively. Based on the present results, we recommend cardiac thrombus be investigated by transesophageal echocardiography in cases of atrial fibrillation accompanied by recurrent thromboembolism. This should be followed by thrombectomy under cardiopulmonary bypass, even in the elderly.