We report herein the case of a 64-year-old man who underwent urgent surgery for a huge abdominal aortic aneurysm (AAA) with severe lumbago. At surgery, a defect in the posterior wall of the AAA, through which the adjacent lumbar vertebrae was seen after removal of intraluminal thrombi, was encountered with no evidence of blood leakage. This is a rare case of AAA that eroded the posterior wall and exposed the vertebrae.