A 67-year-old man who had undergone robot-assisted laparoscopic radical prostatectomy 16 days before suffered from high fever. A screening CT showed an aortic arch aneurysm was 40 mm in diameter, and Bacteroides fragilis was identified from blood culture. A few days after the first CT, the size of the aneurysm increased rapidly to 50 mm in diameter, subsequently an urgent procedure of total arch replacement using rifampicin-soaked Dacron graft was performed. Although the postoperative course was unremarkable, pyrexia recurred on the ninth post operative day. The third CT showed a new aneurysm in the thoraco-abdominal aorta just below the celiac artery. The second urgent procedure of graft replacement of the thoraco-abdominal aorta with the reconstruction of the celiac artery was performed. Preoperative FDG-PET/CT was useful to decide the level of the resection and the suture. The intravenous administration of the antibiotics continued for six weeks after surgery. The patient is doing well without any signs of infection on oral antibiotics at 7 months after the second surgery.