A head protecting airbag is folded up to be housed at an upper part of a
window of a vehicle so as to be deployed and inflated downward from the
upper part of the window so as to cover an interior side of the window.
In the airbag, a plurality of parallel cells adapted to be deployed and
inflated by an inflating gas introduced thereinto are provided in
parallel with each other below a gas supply passage portion in which the
inflating gas flows along a longitudinal direction. In a cell of the
parallel cells so provided which is required to deploy quickly, of front
and rear partitioning portions, a partitioning portion situated at an
upstream side of the gas flowing in the gas supply passage portion is
provided such that an end thereof which extends upward from a lower edge
portion is disposed so as to form an inlet port between a distal end of a
horizontal portion of a downstream side partitioning portion and itself.