An extremely easy-to-play keyboard for musical instrument capable of forming any keyboard rows such as a semitone arrangement to a diatessaron arrangement and a chord arrangement with one keyboard substrate, wherein the keyboard substrate is formed so that the keyboard is formed by disposing, parallel with each other, a large number of key substrates (1) extending in the longitudinal direction of the keyboard with a difference of semitone, installing a plurality of key top mounting parts (5) on each key substrate (1) in the longitudinal direction, and installing the key tops (4) on any key top mounting parts, or by combining various types of keyboard rows with each other, or disposing the keys positioned adjacent laterally to each other in all or a part of the keyboard rows with a difference of minor third and those positioned adjacent longitudinally to each other with a difference of whole tone in the direction from the front side to the right rear side.