To connect synthetic resin sheets constituting an air bag together very firmly.

In an air bag 1, a round front panel 2 made of a synthetic resin sheet, a round rear panel 3 which is made of a synthetic resin sheet and is provided with an inflator insertion opening 4 in the center, are connected together by means of a connecting resin 5. The circumferential edge part of the front panel 2 is protruded outward from the circumferential edge part of the rear panel 3. In the front panel 2, the connecting resin 5 is connected to the end face and to the inside face. In the rear panel 3, the connecting resin 5 is connected to the end face and to the outside face. In the corner angle part in which the outer circumferential face of the connecting resin 5 and the rear panel 3 side face cross each other, a recessed stepped part is extended along the outer circumferential face.