A support assembly of a keyboard apparatus activated in accordance with pressing of a key to rotate a hammer provided at one end of a hammer shank, the support assembly includes a support rotatably disposed with respect to a frame, a jack having one side rotatably connected to the support and another side including a contact surface which makes contact with a hammer shank roller provided to the hammer shank, and a rib provided to the other side of the jack and projecting to a hammer shank roller side of the contact surface.