A grand piano has a built-in music rack for keeping a music score book thereon, and the built-in music rack includes a guide laterally extending inside the piano cabinet and a desk board projecting over the piano cabinet and connected to the guide; when a pianist exerts force on the desk board, the guide permits the desk board to slide laterally so that the pianist can easily adjust the music score book to a proper position; since most of the guide is hidden inside the piano cabinet, the pianist feels the grand piano same in external appearance as a standard grand piano.