A single coronary artery is a rare congenital anomaly of the coronary arteries where only one coronary artery arises from the aortic trunk by a single coronary ostium, supplying the entire heart. We report a case of a 70 years-old man with mitral valvular insufficiency and atherosclerotic right and left circumflex coronary arteries, in whom coronary angiography showed a single coronary artery arising from a single ostium in the right sinus of Valsalva (R-II-B subtype) and transverse trunk coursed between aorta and pulmonary artery. The clinical significance and subtype of the single coronary artery are discussed.