A key structure which has a key formed by a wood part so as to present a woody appearance and which makes it possible to prevent support members thereof that support the wood part from being damaged during machining of the wood part for width adjustment. The key structure functions as a key pivotally moved by key depression when it is mounted in a keyboard apparatus. A wood part includes a narrow part having opposite lateral sides. An elongated upper plate body has opposite lateral sides, and fixedly supports the wood part. Recessed parts are formed in the respective lateral sides of the upper plate body at least in a substantial entirety of a region of the upper plate body in a longitudinal direction of the key structure where the wood part does not exist. The recessed parts are recessed laterally inward of the respective lateral sides of the narrow part of the wood part.