An intrathoracic mass that manifested compression sign of large vessel and heart by mass was confirmed as huge sinoatrial nodal artery aneurysm and resection of aneurysm was performed. Preoperative precise diagnosis of coronary artery aneurysm is difficult because the most coronary artery aneurysm is incidentally confirmed during diagnostic coronary angiography or autopsy. So huge coronary artery aneurysm which manifests compression sign of large vessel and heart by the mass may be misdiagnosed as simple mediastinal mass. We reports huge coronary artery aneurysm that manifested compression sign of large vessel and heart by the mass with reviews of anesthetic management and diagnostic approach.