A knee airbag device includes a knee airbag that is disposed in a folded state inside a steering column cover. When the knee airbag receives gas, the knee airbag is inflated and deployed from the inside of the steering column cover toward the knee portion of an occupant. The knee airbag includes an instrument panel-side foundation cloth positioned close to an instrument panel when the knee airbag is deployed, an occupant-side foundation cloth positioned close to the occupant when the knee airbag is deployed, and a first strap and a second strap that connect the instrument panel-side foundation cloth and the occupant-side foundation cloth. When the knee airbag is deployed, the first strap is positioned above the second strap and the length of the first strap in a vehicle-longitudinal direction is set to be larger than the length of the second strap in the vehicle-longitudinal direction.
