Anomalous origin of the left coronary artery from the right sinus of Valsalva is a rare anomaly known to cause sudden death in young competitive athletes. We report a case of 58-year-old male who was admitted to our hospital because of acute coronary syndrome. Emergency coronary angiography documented a critical stenosis in the right coronary artery. A cardiologist implanted a stent with good angiographic result. It was not possible to place a catheter in left coronary artery ostium at normal position. The patient was diagnosed to have an anomalous origin of the left coronary artery arising from the right sinus of Valsalva, passing between the aorta and the main pulmonary artery by coronary 3 dimensional computed tomography angiography (3D-CTA). After a stent insertion, he still had angina. Further examination of the left coronary artery including intravascular ultrasound revealed a hard plaque in the left main trunk as the culprit lesion. Because previous percutaneous coronary intervention was ineffective, off-pump coronary artery bypass grafting was performed using bilateral internal thoracic arterial grafts to the left anterior descending artery and the obtuse marginal branch. Postoperative 3D-CTA demonstrated patent grafts. Two years after the operation, he is free from chest discomfort.