A keyboard device for a keyboard instrument includes a keyboard chassis, a key disposed on the keyboard chassis, and a key support mechanism which supports the key from below and causes the key to operate such that the key pivotally moves about a virtual pivot. One of a first arm rear-side connecting portion and a second arm front-side connecting portion includes an engagement shaft extending in a left-right direction, and the other of them includes an engagement recess which has a U shape in side view and open in one of a front direction and a rear direction and is engaged with the engagement shaft. A cushioning member in sliding contact with an inner surface of the engagement recess is mounted on the engagement shaft in a state covering an outer peripheral surface of the engagement shaft.