A keyboard device for an electronic keyboard instrument, including several keys arranged side by side in a left-right direction, a hammer support disposed rearward of the keys, a plurality of hammers pivotally supported by the hammer support to be pivotally moved in accordance with key depression, and a key switch having a plurality of switch bodies provided in association with the respective hammers and a switch board mounted to the hammer support. The hammer support has a hammer supporting part for supporting the hammers and a switch mounting part to which the key switch is mounted, and is formed by an injection molded article of a predetermined kind of synthetic resin.