We report a case of pseudoaneurysm formation after aneurysmal clipping. An aneurysm, which was located on the beginning of orbitofrontal artery, was clipped and wrapped with $Surgicel^{(R)}$ and fibrin glue. Four weeks later, an enlarged aneurysm was detected at the same site on postoperative angiography. We could not find a new aneurysm in the second operation except inflated wrapping region. And clip had been slipped from the original aneurysmal neck. So we concluded that a new aneurysm was a pseudoaneurysm made with surgicel and fibrin glue. And it had been formed from continuous minor leakage caused by slipped clip.