A key unit having a white key unit and a black key unit in which main bodies of a plurality of white keys and black keys, respectively, are coupled to respective common key support parts via coupling parts pivotably in a key depression direction is mounted on a keyboard frame. In the black key unit, a total width in a key arrangement direction of each of the coupling parts is wider than a key width of the black key main body, whereby the coupling parts restrict yawing in a key width direction when the black keys are depressed/released. In the white key unit, each of the coupling parts is narrower in total width in the key arrangement direction than each of the coupling parts in the black key unit, and guide parts are provided on free end sides of the white keys to restrict yawing in the key arrangement direction.