An airbag restraint system for protecting a vehicle passenger in the event of a serious vehicle collision. The airbag is comprised of an airbag which is adapted to inflate upon being supplied with gas from a gas generator. The airbag includes a bag-shaped section which has generally circular rear and front side sheet members which are joined together at their peripheral portions to define a gas chamber to be filled with the gas from the gas generator. A plurality of suspension belts are disposed inside the bag-shaped section. One end of each suspension belt is sewed to a belt catch member which is in turn sewed to the central part of the rear side sheet member, thereby forming a sewed section. The sewed section extends linearly and includes a straightly extending portion which is generally perpendicular to a lenghwise direction of each suspension belt.