Pulsating flow within an elastic cerebral aneurysm model was visualized by particle image velocimetry (PIV) to clarify the effect of wall elasticity on flow instability and wall shear stress(WSS). In the experiment, we used a full - scaled patient - specific cerebral aneurysm phantom with a thin transparent silicone wall fabricated by soaking a plaster mold. In order to clarify the effect of elastic deformation, a comparison was made with an experiment conducted while suppressing volumetric deformation by applying pressure. The results showed that in the middle plane, the wall deformation reduced the maximum TKE by about 26% and the average TKE by about 22% in comparison with the less - deformation model. In addition, the wall deformation reduced the maximum WSS by about 13% and the average WSS by about 17% in comparison with the less - deformation model. This finding suggests that the wall deformation of cerebral aneurysm attenuates flow turbulence and affects the magnitude of WSS.