KNEE AIRBAG DEVICE

To provide a knee airbag device in which it is difficult for an airbag cushion to enter between knees of an occupant during expansion and deployment, and that can stably restrain a knee from a front side.A knee airbag device 10 includes: an airbag cushion 11; a storage case 15 in which is formed a horizontally long opening part 16 where the expanded and deployed airbag cushion 11 pops out; a first flap 21 for covering the airbag cushion 11 exposed through the opening part 16 such that the airbag cushion 11 is retained in the storage case 15, and having a first weak part 31 that breaks when pressed by the airbag cushion 11 during expansion and deployment; and a second flap 22, which is a component with a larger dimension in a length direction than the first flap 21 and for covering an outer surface of the first flap 21 so as to transverse in a short direction of the opening part 16 a center part 11c of the airbag cushion 11 in a lateral direction, the second flap having a second weak part 32 that breaks when pressed by the airbag cushion 11 after rupture of the first weak part 31.