A keyboard instrument such as an electronic piano comprises a keyboard structure that is basically identical to the keyboard structure of an upright piano except hammer assemblies and a struck portion attached to an action bracket. Each of the hammer assemblies is constituted by a hammer shank and a pseudo hammer, one of which is used to strike the struck portion having a multilayer structure including an elastic member (e.g., a plate spring) sandwiched between buffer materials. The elastic member has a prescribed number of striking areas in correspondence with keys arranged on a keybed, wherein the striking areas are gradually increased in weights and bends (or deflections) in a pitch descending order from higher pitches to lower pitches. Thus, it is possible to simulate weight factors and bends (or deflections) of strings actually struck by hammer felts in an upright piano.