A keyboard apparatus of an electronic musical instrument has a plurality of pivoting members (white key main body 1, black key main body 2, and massive body 28) which pivot in response to depression or release of keys, a frame 3 which supports the pivoting members, and action restricting members (lower limit stopper 5 and upper limit stopper 6) which cause collision thereof with the pivoting members to restrict a range in which the pivoting members are allowed to pivot. The action restricting member contains a plurality of grains 11 in an enclosure member 12, and is arranged, in a state where inflow and outflow of air are allowed between the closed area and outside air, at the frame's side.