To house a keyboard lid effectively utilizing space inside of an instrument main body while covering a keyboard with the minimum size of keyboard lid.

A wind-up roller 61 is arranged in a housing part S1 formed among a rear part 20a1 of a white key main body 20a, connection part 40a1 of a black key main body 40a and a top board 66 in up and down direction, between an attachment part 68 and a front board part 64 in back and forth direction. When a bar-shaped member 63 is grasped and pulled forward, a sheet lid 62 is pulled out forward from an opening part 65 of the front board part 64 against an energizing force in the wind-up direction of the wind-up roller 61 and becomes a closed lid state to cover the whole keyboard KB. On the other hand, when opening the lid, the bar-shaped member 63 is grasped and the sheet lid 62 is wound with the wind-up force of the wind-up roller 61. When the bar-shaped member 63 is abutted on a front face near the opening part 65 of the front board part 64, the sheet lid becomes a wind-up state to be housed.