Keyboard apparatus includes: a plurality of white and black keys: a plurality of mass body units each pivotable in response to operation of a corresponding one of the keys; a frame having mounted thereon the plurality of keys and mass body units; and upper- and lower-limit stoppers provided on the frame for limiting a pivotable range of each of the mass body units by the mass body unit colliding against the stoppers. Each of the mass body units includes a cavity portion provided in a section thereof that pivots against a gravitational force as the corresponding key is depressed, and a plurality of particles are accommodated in the cavity portion with some vacant space left in the cavity portion.