A keyboard device for an electronic keyboard instrument, which enables facilitation of work for mounting and dismounting a key switch and install hammers and the key switch with high accuracy, and provision of a touch feeling similar to one provided by an acoustic grand piano while keeping the device compact in depth. The device comprises swingable keys, a hammer support formed by a synthetic resin molded article, hammers pivotally supported by the hammer support, and a key switch including switch bodies provided in association with the hammers and a switch board. The hammer support has a switch mounting part formed with an opening vertically extending therethrough. The key switch is removably mounted to the switch mounting part, with the switch bodies facing the hammers from above via the opening and the switch board placed on the upper surface of the switch mounting part.