A keyboard apparatus which is capable of enhancing key touch feeling. The keyboard apparatus has a chassis (1), and key bodies (10) to be depressed are supported by the chassis. A hammer body (20) associated with each of the key bodies is driven by the key body via engagement with the same to move in a key depressing direction to thereby impart an inertial force to the key body when the key is depressed. The state of engagement between the key body and the hammer body suddenly changes as the key depressing velocity changes across a predetermined key depressing velocity, such that when the key depressing velocity is higher than the predetermined key depressing velocity, the hammer body hardly moves in the key depressing direction, whereas when the key depressing velocity is not higher than the predetermined key depressing velocity, the hammer body moves in the key depressing direction.