An air-bag device in which a deployed air-bag has a complete deployment portion positioned on the longitudinally central side and having a substantially constant diameter and incomplete deployment portions positioned on longitudinally opposite end sides and having a diameter that gradually decreases in going toward a blocking member, the incomplete deployment portion has high rigidity compared with the complete deployment portion and is difficult to deform when there is a collision with a pedestrian, thus degrading the impact absorption performance, but disposing the plurality of vent holes in the incomplete deployment portion at a fixed pitch in the longitudinal direction and the circumferential direction of the air-bag enables the rigidity of the incomplete deployment portion to be lowered and the impact absorption performance to be enhanced, thereby giving uniform impact absorption performance over the entire longitudinal length of the air-bag.