An airbag apparatus , comprising: an airbag configured to restrain a passenger in a vehicle when expanded and deployed; a gas generator for generating expansion gas which expands and deploys the airbag ; and an active vent mechanism which is provided in the airbag and is capable of discharging gas from inside the airbag ; wherein the active vent mechanism comprises: a first vent hole formed in the airbag; a patch capable of releasing and closing the first vent hole in accordance with the internal pressure of the airbag , with a portion of the patch coupled to the outer surface of the airbag ; a coupling member having one end coupled to the patch , with the other end entering the airbag and coupled to the airbag ; an opening provided in the vicinity of the first vent hole , with a portion of the patch or a portion of the coupling member penetrating through the opening; ; and a releasing means for reducing the tension of the coupling member; wherein, when the airbag is fully deployed, the patch is operable so as to block the first vent hole via the tension of the coupling member , while when the releasing means reduces the tension of the coupling member , the patch is operable so as to be separated from the outer surface of the airbag and thereby induce discharge from the first vent hole , characterized in that the active vent mechanism further comprises a substantially cylindrical regulating member into which the coupling member is inserted inside the airbag , wherein the regulating member has: a first end coupled to the inner surface of the airbag so as to surround the opening inside the airbag ; and a second end coupled to the coupling member in a sealed state. an airbag configured to restrain a passenger in a vehicle when expanded and deployed; a gas generator for generating expansion gas which expands and deploys the airbag ; and an active vent mechanism which is provided in the airbag and is capable of discharging gas from inside the airbag ; wherein the active vent mechanism comprises: a first vent hole formed in the airbag; a patch capable of releasing and closing the first vent hole in accordance with the internal pressure of the airbag , with a portion of the patch coupled to the outer surface of the airbag ; a coupling member having one end coupled to the patch , with the other end entering the airbag and coupled to the airbag ; an opening provided in the vicinity of the first vent hole , with a portion of the patch or a portion of the coupling member penetrating through the opening; ; and a releasing means for reducing the tension of the coupling member; a first vent hole formed in the airbag; a patch capable of releasing and closing the first vent hole in accordance with the internal pressure of the airbag , with a portion of the patch coupled to the outer surface of the airbag ; a coupling member having one end coupled to the patch , with the other end entering the airbag and coupled to the airbag ; an opening provided in the vicinity of the first vent hole , with a portion of the patch or a portion of the coupling member penetrating through the opening; ; and a releasing means for reducing the tension of the coupling member; wherein, when the airbag is fully deployed, the patch is operable so as to block the first vent hole via the tension of the coupling member , while when the releasing means reduces the tension of the coupling member , the patch is operable so as to be separated from the outer surface of the airbag and thereby induce discharge from the first vent hole , characterized in that the active vent mechanism further comprises a substantially cylindrical regulating member into which the coupling member is inserted inside the airbag , wherein the regulating member has: a first end coupled to the inner surface of the airbag so as to surround the opening inside the airbag ; and a second end coupled to the coupling member in a sealed state. <EOS>