A keyboard device for an electronic keyboard instrument, capable of suppressing bouncing of a hammer returning to its original position. A key extends in a front-rear direction swingably about a balance rail pin. The hammer is formed vertically pivotally movable between initial and pivotally-moved positions about a hammer fulcrum provided near a rear end of the key and is placed on the key via a key contact portion in contact with a rear end of upper surface of the key from above, for pivotal motion by swinging of the key. A hammer cushion is provided on upper surface of the key at a predetermined location forward of the key contact portion to suppress bouncing of the hammer by contact with a cushion contact portion of the hammer returning from the pivotally-moved position to the initial position by releasing the key depression.