A knee airbag device includes an airbag module and an airbag door. The airbag module, which is provided inside a column cover that covers the rear end portion of a steering column, includes a gas generation device that generates gas when a collision occurs, and a knee airbag that is inflated and deployed from a folded state when the knee airbag receives the gas from the gas generation device. The airbag door, which is provided in the lower portion of the column cover, is opened when the inflation pressure of the knee airbag is equal to or higher than a predetermined value. When the knee airbag is deployed, at least a portion of the airbag door is positioned between an interfering object that is positioned in an area on the side of the column cover, and at least a portion of the knee airbag.