A keyboard apparatus is including a plurality of keys and a plurality of mass members provided under the respective keys to be pivotably supported on a keyboard frame being a support member, each of the mass members extends along a longitudinal direction of the key and has a mass concentration part in its rear end portion, and when not driven by a mass driving part of the key, each of the mass members is in an inclined state with the mass concentration part being at the lowest descended position. The keyboard frame has a rib provided between two adjacent mass members among the plural mass members, and at least part of a lower edge of the rib is formed along lower edges of the mass members in the inclined state.