AIRBAG DEVICE

An airbag having an exhaust hole and an opening/closing control device configured to control opening and closing of the exhaust hole are provided. The airbag includes a bag body, and a discharge portion having the exhaust hole, the discharge portion is configured to maintain a blocked state of the exhaust hole by being drawn into the bag body at the time of inflation of the bag body in a state where connection between a connection member and the opening/closing control device is maintained, and to be inflated by protruding from the bag body at the time of inflation of the bag body in a state where the connection between the connection member and the opening/closing control device is released to open the exhaust hole. A dummy inflation portion inflated to partially protrude from the bag body is formed at a position approximately symmetrical to the discharge portion. A volume of the dummy inflation portion at the time of inflating completion is set to be smaller than a volume of the discharge portion in a state where the exhaust hole is open at the time of inflation.