A 38-year-old woman with coronary arterial aneurysm, which resulted in myocardial infarction, was reported. By coronary arteriography, an aneurysm of the left anterior descending branch was found, but no arteriovenous shunt could be revealed. The patient has neither clinical history of severe febrile inflammatory disease nor any coronary risk factors. The etiology of her coronary arterial aneurysm was considered to be congenital. The patient underwent aorto-coronary saphenous vein bypass graft surgery successfully. We believe that this is the first case report in Japan on congenital aneurysm of the coronary artery without arteriovenous fistula, which was diagnosed during life by coronary arteriography.