An occupant restraint system includes an airbag having at least one vent hole and an inflator. The airbag is inflated by a gas generated by the inflator when there is a vehicle collision, and deploys into a curtain shape along an inner side face of an occupant compartment. Since the vent holes, through which gas is discharged from an inflatable part of the airbag, are made to open downward at the lower edge of the airbag, not only is it possible to reliably prevent the inflatable part from being excessively inflated, and thereby from becoming hard resulting in a failure to gently restrain an occupant, but also it is possible to prevent the vent holes from being blocked by the vehicle body or an occupant, thus reliably exhibiting a gas discharge function and preventing the gas discharged though the vent holes from directly impinging on the occupant.