A stabilization time of a wake structure behind a hypersonic vehicle is very important in an experiment on the flow structure by using pulsed facilities of high enthalpy or of high Mach number. However, observations themselves of such wake structure have been very difficult, and therefore, the experimental discussion about the stabilization time itself has also been very difficult. In this study the stabilization time of the wake structure was formulated by using the dimensional analysis and the present experimental results. The experiment was carried out by observing separation points and free shear layers just after capsule models similar to a MESUR pathfinder probe. To visualize the wake structure, one of techniques called the electrical discharge method was utilized. From these investigations it was found that the stabilization time of the wake structure was related to the Reynolds number, the model scale, and the freestream velocity. A hypersonic gun tunnel of Mach 10 was used in this experiment.