To provide a head protection air bag device which has no need to deflect the gas discharged from an inflator downward in the head protection air bag device connecting the inflator to an intermediate portion in the vehicle longitudinal direction.

The head protection air bag device is constituted so that it is folded and mounted to the storage portion of the vehicle, and the inflation gas discharged from an inflator to the vehicle longitudinal direction is obliquely downward guided to an inflation shielding part 15 of an air bag body 13 with a gas inflow port 26 of the air bag body 13 and an inflow side part 27a of a straightening fabric 27.