HEAD PROTECTING AIRBAG DEVICE

An airbag includes an annular attachment portion having an opening portion through which a bracket can be inserted and which is open in a substantially square shape. A case includes a protective ring portion having an opening through which the bracket can be inserted and which protects the annular attachment portion. The protective ring portion includes a corner cover portion that covers areas of front and rear corner portions on an upper edge side of an inner peripheral edge of the opening portion.