An airbag apparatus, comprising: a first tether disposed inside an airbag cushion in a forward-backward direction; and at least one second tether disposed inside the airbag cushion in a leftward-rightward direction and connected to the first tether, wherein at least one tether passage having left and right openings is formed in a middle of the first tether, wherein the at least one second tether passes through the at least one tether passage to be connected to the first tether, wherein the at least one tether passage comprises a plurality of tether passages, and the plurality of tether passages is formed in a longitudinal direction of the first tether, wherein the at least one second tether comprises: a 2-1 st tether formed in a rope shape, configured to pass through a front tether passage of the plurality of tether passages, and connected at two ends thereof to front portions of two opposite inner side surfaces of the airbag cushion; and a 2-2 nd tether formed in a rope shape, configured to pass through a rear tether passage of the plurality of tether passages, and connected at two ends thereof to rear portions of the two opposite inner side surfaces of the airbag cushion, wherein the airbag apparatus further comprises: a partition wall formed inside the at least one tether passage in the leftward-rightward direction and configured to divide the at least one tether passage into a plurality of sub-passages, wherein when the airbag cushion is deployed, a width of the airbag cushion is configured to be limited in the leftward-rightward direction by the first tether tensioned in the forward-backward direction and a portion of the at least one second tether is configured to be pulled toward a passenger, and wherein, when the passenger comes into contact with the airbag cushion, the first tether is configured to be loosened, and the portion of the at least one second tether is configured to be moved away from the passenger. a first tether disposed inside an airbag cushion in a forward-backward direction; and at least one second tether disposed inside the airbag cushion in a leftward-rightward direction and connected to the first tether, wherein at least one tether passage having left and right openings is formed in a middle of the first tether, wherein the at least one second tether passes through the at least one tether passage to be connected to the first tether, wherein the at least one tether passage comprises a plurality of tether passages, and the plurality of tether passages is formed in a longitudinal direction of the first tether, wherein the at least one second tether comprises: a 2-1 st tether formed in a rope shape, configured to pass through a front tether passage of the plurality of tether passages, and connected at two ends thereof to front portions of two opposite inner side surfaces of the airbag cushion; and a 2-2 nd tether formed in a rope shape, configured to pass through a rear tether passage of the plurality of tether passages, and connected at two ends thereof to rear portions of the two opposite inner side surfaces of the airbag cushion, wherein the airbag apparatus further comprises: a partition wall formed inside the at least one tether passage in the leftward-rightward direction and configured to divide the at least one tether passage into a plurality of sub-passages, wherein when the airbag cushion is deployed, a width of the airbag cushion is configured to be limited in the leftward-rightward direction by the first tether tensioned in the forward-backward direction and a portion of the at least one second tether is configured to be pulled toward a passenger, and wherein, when the passenger comes into contact with the airbag cushion, the first tether is configured to be loosened, and the portion of the at least one second tether is configured to be moved away from the passenger. a 2-1 st tether formed in a rope shape, configured to pass through a front tether passage of the plurality of tether passages, and connected at two ends thereof to front portions of two opposite inner side surfaces of the airbag cushion; and a 2-2 nd tether formed in a rope shape, configured to pass through a rear tether passage of the plurality of tether passages, and connected at two ends thereof to rear portions of the two opposite inner side surfaces of the airbag cushion, wherein the airbag apparatus further comprises: a partition wall formed inside the at least one tether passage in the leftward-rightward direction and configured to divide the at least one tether passage into a plurality of sub-passages, wherein when the airbag cushion is deployed, a width of the airbag cushion is configured to be limited in the leftward-rightward direction by the first tether tensioned in the forward-backward direction and a portion of the at least one second tether is configured to be pulled toward a passenger, and wherein, when the passenger comes into contact with the airbag cushion, the first tether is configured to be loosened, and the portion of the at least one second tether is configured to be moved away from the passenger.