A keyboard device for a keyboard instrument, which can be manufactured by a simplified manufacturing process and at reduced manufacturing costs, is disclosed. A keyframe is formed by a molded piece of a synthetic resin. A plurality of front rail pins and a plurality of balance rail pins are arranged in a juxtaposed manner in a left-right direction at a front part and a central part of the keyframe in a front-rear direction. A plurality of keys are made of wood and each have a balance rail pin hole formed in a central portion thereof in the front-rear direction. The keys are swingably supported on the keyframe in a state where the balance rail pins are each engaged with the balance rail pin hole associated therewith and at the same time the keys are prevented from being swung in the left-right direction by the front rail pins associated therewith.