A knee airbag device for a vehicle, configured in such a manner that, when a knee airbag is inflated and expanded with the knees of a vehicle occupant located close to an airbag door, a load to the lower legs is reduced. A first tear section (100) for expanding a first airbag door (108) in the vehicle's top-bottom direction and a second tear section (102) for expanding a second airbag door (112) in the vehicle's lateral direction are formed on the rear surface side of a glove-box-door outer member (24). The first tear section (100) is composed of a left and right pair of vertical tear sections (104) and a first horizontal tear section (106). The second tear section (102) is composed of second lateral tear sections (110).