To provide an air bag used for a vehicle collision experiment for easily and accurately recording the relative position, when a dummy doll collides with an air bag.

When the vehicle collision experiment of the air bag 1 is performed by using the dummy doll, a microcapsule 3, in which an inclusion where an adhesion mark remains is sealed, is mounted on the surface of the air bag 1, so that the microcapsule 3 is broken at a part in which the dummy doll interferes with the air bag 1 by the vehicle collision experiment and the inclusion is leaked; and the leaked inclusion adheres to the surface of the air bag 1 and the dummy doll, thus allowing the relative position at the interference between the dummy doll and the air bag 1 to appear accurately.