An airbag for a passenger seat is folded and stored in a storage so as to be deployed towards the passenger seat in such a manner as to enlarge towards the left and right when exiting the storage. The airbag includes a bag body that includes a mount-side portion to be mounted on the storage, and a cover panel that is made of a flexible sheet-shaped material and covers an outer circumference of the mount-side portion of the bag body. The cover panel is configured to cover an edge of a peripheral member of the storage at least in left and right sides of the storage at airbag deployment. The cover panel is joined to the bag body in such a manner that its edge portion is capable of slipping relative to the bag body at least in the left and right portions.