In this article the freely oscillating 3-dimensional parachute-like body sustained at one point is focused. To catch the real phenomenon by numerical simulation, the virtual mass is considered in this study. The flow field is calculated by using the MAC method applying third order upwind scheme for the convex term, and applying central difference for the other terms. ALE method is applied in order to consider a moving boundary problem. The virtual mass is calculated by using a potential flow at every time step. As a result, it has been made clear that the virtual mass has influence on the freely oscillating rigid concave body motion. And the flow structure around the freely oscillating parachute-like body is made clear.