The purpose of this study is to develop covered stent what is able to treat endovascular aneurysm. It was a structural characteristic that thin cover film with stent have microporous. Until now in vivo experiment, increasing the aperture ratio of covered stent from 12.6% to 23.6%, it was possible that coexistence of reliable to embolize the aneurysm and to inhibit the intimal hypertrophy. Furthermore, we expect to form the intima early and to inhibiti of intimal hypertrophy by increasing of aperture ratio. However it is concerned to constrict the thrombus formation. In this study, we investigate the influence on intra-aneurysm flow of varying aperture ratio of multi-pore film by flow visualization of aneurysm model in vitro.