A 60-year-old man complained of palpitation due to transitory atrial fibrillation. The annulo-aortic ectasia was recognized, and was getting enlarged to 52 mm. After an additional examination, membranous ventricular septal aneurysm was revealed. There was no evidence of thrombus, shunt, or infection in the membranous ventricular septal aneurysm. The valve-sparing aortic root replacement (reimplantation) and the patch-closure of the membranous ventricular septal aneurysm were performed. Stabilizing the subannular tissue by a Dacron patch made the reimplantation technique feasible. To secure a subannular suture line, 3 mattress stitches were passed inside-out through the Dacron patch, the fibrous rim of the membranous septum and the prosthetic graft again. He was discharged without any complication 12 days after the operation.