A 14-year old boy was admitted with stuporous mentality. CT scan, MRI and cerebral angiogram revealed SAH and a giant aneurysm of right middle cerebral artery($4{ imes}5{ imes}5.3cm$). To minimize surgical risk, endovascular treatment was done with MDS(mechanical detachable system)-spiral coil. Follow up MRI showed intraluminal thrombus formation of the aneurysm.