A flexible aeroshell for atmospheric entry vehicles has attracted attention as an innovative space transportation system because the aerodynamic heating during an atmospheric entry can be reduced dramatically due to its low ballistic coefficient. We have researched and developed a capsule-type vehicle with a flare-type membrane aeroshell sustained by an inflatable torus frame. One of the key technologies is to develop a large and low-mass aeroshell including inflatable structures. As a part of the development, a miniature experimental vehicle was developed and a balloon drop test was carried out in order to acquire the vehicle with inflatable structures in a high altitude and a free flight condition. The diameter, the total mass, and the ballistic coefficient of the experimental vehicle are 1.264m, 3.375kg, and 2.69kg/m2, respectively and its aeroshell consists of a thin membrane flare made of nylon and a torus which can be inflated by gas pressure. The inflatable aeroshell was deployed and the experimental vehicle was separated from the balloon at an altitude of 25km. After the separation, the vehicle flied 30 minutes until a splashdown. This balloon test is very successful and fruitful and following results were achieved. 1) Remote deployment system of the inflatable aeroshell by sending a command from a ground station worked well. 2) The flight trajectory, the aerodynamic characteristics and the vehicle attitude were obtained by post flight analysis of the flight data. 3) As for a structural strength of the inflatable aeroshell, valuable data were obtained which can be compared with preliminary structural analysis. In this test, we could not only demonstrate the stable flight but also acquire the various knowledge about the thin membrane aeroshell sustained by the inflatable structure, which can not be obtained only in the ground test.