A method of controlling an airbag inflator apparatus, the method comprising: determining, by a controller, when a weight of an occupant is in one of predetermined weight ranges sequentially allocated by the controller, while the occupant is accommodated on a seat; performing, by the controller, a first logic for operating the airbag inflator apparatus at a lowest first intensity among predetermined intensities when it is determined that the weight of the occupant is in a lightest first weight range among the predetermined weight ranges: and performing, by the controller, a second logic for operating the airbag inflator apparatus at an intermediate second intensity among the predetermined intensities or a third logic for operating the airbag inflator apparatus at a highest third intensity among the predetermined intensities by the controller, according to conditions including a position of the seat, a state of operation of a recliner, a collision condition, a collision pulse, and wearing of a belt, when it is determined by the controller that the weight of the occupant is in third or fourth weight range among the predetermined weight ranges; wherein the collision condition is determined as a high-speed collision when an average value of collision acceleration for a predetermined first reference time in an initial stage of vehicle collision is equal to or greater than a predetermined reference acceleration; wherein the collision condition is determined as a low-speed collision when the average value of collision acceleration is less than the predetermined reference acceleration; wherein the collision pulse is determined as a normal pulse when a rising gradient of collision acceleration during a predetermined second reference time in an initial stage of vehicle collision is equal to or greater than a predetermined reference gradient; wherein the collision pulse is determined as a delay pulse when the rising gradient of collision acceleration is less than the predetermined reference gradient; and wherein in the performing a second logic or a third logic, when the seat is disposed forward, the controller is configured to determine a collision condition for high-speed collision or low-speed collision according to a magnitude of collision acceleration, in which case the controller is configured to determine a collision pulse when the collision condition is determined as the high-speed collision, so that the second logic is performed when the collision pulse is a delay pulse, but the third logic is performed when the collision pulse is a normal pulse. determining, by a controller, when a weight of an occupant is in one of predetermined weight ranges sequentially allocated by the controller, while the occupant is accommodated on a seat; performing, by the controller, a first logic for operating the airbag inflator apparatus at a lowest first intensity among predetermined intensities when it is determined that the weight of the occupant is in a lightest first weight range among the predetermined weight ranges: and performing, by the controller, a second logic for operating the airbag inflator apparatus at an intermediate second intensity among the predetermined intensities or a third logic for operating the airbag inflator apparatus at a highest third intensity among the predetermined intensities by the controller, according to conditions including a position of the seat, a state of operation of a recliner, a collision condition, a collision pulse, and wearing of a belt, when it is determined by the controller that the weight of the occupant is in third or fourth weight range among the predetermined weight ranges; wherein the collision condition is determined as a high-speed collision when an average value of collision acceleration for a predetermined first reference time in an initial stage of vehicle collision is equal to or greater than a predetermined reference acceleration; wherein the collision condition is determined as a low-speed collision when the average value of collision acceleration is less than the predetermined reference acceleration; wherein the collision pulse is determined as a normal pulse when a rising gradient of collision acceleration during a predetermined second reference time in an initial stage of vehicle collision is equal to or greater than a predetermined reference gradient; wherein the collision pulse is determined as a delay pulse when the rising gradient of collision acceleration is less than the predetermined reference gradient; and wherein in the performing a second logic or a third logic, when the seat is disposed forward, the controller is configured to determine a collision condition for high-speed collision or low-speed collision according to a magnitude of collision acceleration, in which case the controller is configured to determine a collision pulse when the collision condition is determined as the high-speed collision, so that the second logic is performed when the collision pulse is a delay pulse, but the third logic is performed when the collision pulse is a normal pulse.