To be useful as the protection of a human body head part and the back of the neck from falling objects at the time of an earthquake and as a life buoy at the time of a drowning accident.

An air bag 4 is constituted so as to integrally form this hood 2 continuously at the back side top part of a sack main body 1, provide an automatic gas filling device 9 on the inner side of the hood 2 and be the form of covering the human body head part and the back of the neck when gas is filled. Then, the air bag 4 is freely attachably and detachably attached by a Velcro tape (R) or the like, the sack main body 1 is provided with the housing part 3 of the hood 2 and the air bag 4 and the back carrying cord 5 of the sack main body 1 is provided with the housing part 7 freely openable by the 'magic tape (R)' or the like selectively further. Then, the air bag 6 provided with the automatic gas filling device 9 whose one end is fixed to the sack main body is housed in the housing part.