A keyboard apparatus includes: a key; a hammer assembly; a first member having a step; a second member slidable relative to the first member and configured to be moved in a direction in which the second member moves over the step, when the key is pressed; and a third member configured to guide the second member such that the second member is not located at a distance greater than or equal to a predetermined distance from the first member. The third member has a shape at a region of the third member such that the third member does not contact the second member in a state in which the second member is in contact with the first member. When the second member moves over the step, the region is opposed to the second member in the direction in which the second member moves over the step.