A keyboard device is designed for use in an electronic musical keyboard instrument, and composed of a key frame and at least one key array unit mounted in the key frame. The key array unit has a plurality of keys and a common base part which integrates the plurality of the keys and which is fixed to the key frame. The key is composed of a key body having a front end portion, a rear end portion and a top face portion extending between the front end portion and the rear end portion, and a key supporting part which supports the key body in a vicinity of the rear end portion thereof for allowing the key body to pivot around the key supporting part when the top face portion of the key body is pressed downward and which couples the key body integrally to the common base part. The key supporting part is formed below a back of the top face portion of the key body at a position spaced from the rear end portion of the key body toward the front end portion of the key body.