A keyboard apparatus includes a key, a frame, a flexible section configured to rotate the key with respect to the frame, the flexible section having a longitudinal direction, and including a region where a length of the flexible section in a first direction continuously increases toward a first end and a second end of the flexible section in a cross section perpendicular to the longitudinal direction of the flexible section, and a first supporting section supporting side closer to the first end than the region, the first supporting section including a bonding section bonded to the first end, the bonding section including a first section and a second section, the first section and the second section keeping continuity with the flexible section, and a recessed section being arranged at a position, in a scale direction and sandwiched between the first section and the second section, of the bonding section.