A key structure which is free from separation between a wood part thereof and a key base body to which the wood part is secured and has enhanced vertical rigidity in the vicinity of a clearance between the base end of the key base body and the wood part. In the key structure, the key base body has an extended part formed integrally with the base end and extended forward therefrom. The wood part is fixedly bonded to the upper surface of the extended part. A clearance is formed transversely of the key base body between the wood part and the base end. An upper plate body is fixedly bonded to both the upper surface of the wood part and the upper surface of the base end, and the rear part of the upper plate body extends in a manner spanning the base end and the wood part above the clearance.