An airbag is disclosed, including a main bag section deployable in front of a passenger seat, a center bag section which is deployable in such a manner as to protrude towards an inboard side in a vehicle width direction out of the main bag section to an area beneath the rearview mirror. The center bag section includes, on the upper portion as deployed, a region that faces the rearview mirror in an up and down direction. The center bag section internally includes a regulating tether that is disposed generally along an up and down direction and connects the region of the upper portion of the center bag section facing the rearview mirror at airbag deployment and a region of a lower portion of the center bag section deployed beneath the region facing the rearview mirror in order to prevent contact between the center bag section and the rearview mirror.