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 (24, 124) 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 (24, 124) 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 (24, 124), while when the releasing means reduces the tension of the coupling member (24, 124), 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 (24, 124) 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 (24, 124) 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 (24, 124) 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 (24, 124) 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 (24, 124) 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 (24, 124) 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 (24, 124), while when the releasing means reduces the tension of the coupling member (24, 124), 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 (24, 124) 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 (24, 124) in a sealed state.