In a safety bag device for use in a vehicle and of the type wherein a rupture plate is interposed between a high pressure gas container and a conduit leading to an inflatable safety bag. A nozzle having a plurality of nozzle holes opened into the conduit is interposed between the rupture plate and the conduit. A spool is slidably fitted to the nozzle in such a way that it may normally close a predetermined number of nozzle holes, but may be displaced away from the nozzle to open them in response to the increase in pressure in the nozzle chamber when the rupture plate is ruptured in case of a collision, whereby the flow rate of the high pressure gas flowing into the inflatable safety bag may be suitably controlled so as to prevent very rapid expansion of the bag resulting in the injury to an occupant.