A 48-year-old female who was diagnosed as having a right aortic arch with retroesophageal left subclavian artery and left ligamentum arteriosus was referred to our hospital for an aortic arch and descending aortic aneurysm with a dilated Kommerell's diverticulm. This aneurysm was 67mm in maximum diameter, between the aortic arch and the midportion of the descending aorta. Successful surgical treatment was accomplished with the use of extraanatomic bypass grafting between the ascending aorta and the descending aorta and reconstruction of the four main branches of the aortic arch. Postoperative digital subtraction angiography and enhanced CT revealed slight leakage at the distal stump of the aneurysm. Theoretically, resection of the aneurysm and aortic reconstruction would have been the best procedure. However, the complicated anatomy made it difficult to perform total resection of the aneurysm and aortic reconstruction, and several problems remained after operation.