An air bag system is provided wherein a support belt for coupling an airbag to a vehicle body is accommodated in an accommodation part provided in the vehicle body. A belt cover is engaged from above so as to cover the accommodation part. The belt cover is configured to be removed from the accommodation part along with swelling and expansion of the airbag. A wire is coupled to the vehicle body inside the accommodation part so as not to be moved apart from the vehicle body over a predetermined length at the time of removing. The wire is arranged inside the accommodation part, and is coupled to a fixation plate to be connected to a frame of the vehicle body. By inserting the wire into through-holes of the fixation plate, the wire is coupled to the vehicle body, and both ends thereof are connected to the belt cover.