A driver airbag 1 is formed by sewing a front panel 2 and a rear panel 3 together. The rear panel 3 has a horizontal first tuck portion 21, a second tuck portion 22 extending from a right upper side toward a left lower side, and a third tuck portion 23 extending from a left upper side toward a right lower side. The tuck portion 22 and the tuck portion 23 intersect in an upper part of the rear panel 3. Since most of the second and third tuck portions 22, 23 are located in an upper half section of the rear panel 3, the upper part of the driver airbag 1 has a larger thickness than that of a lower part when the driver airbag 1 is inflated completely.