A 59-year-old man underwent an aorto-bifemoral bypass operation for aorto-iliac arteriosclerotic occlusive disease. The total aortic occlusion time was 38min. Soon after the operation, the patient was found to have motor and sensory loss between right L2 and S1, which did not improve. We considered that spinal cord damage was caused by occlusion of the lumbar artery as a result of side clamping of the atherosclerotic abdominal aorta. Therefore, side clamping of the atherosclerotic aorta should be avoided to prevent this serious complication.