Rotation mechanism and keyboard apparatus

A rotation mechanism comprising:

• a shaft portion;
• a bearing portion configured to rotate with respect to a predetermined axis as a center of rotation and configured to slide relative to an outer periphery of the shaft portion;
• a stopper integrally formed with the bearing portion;
• a stopper-contacting portion disposed between the shaft portion and the stopper, the stopper-contacting portion being configured to contact the stopper in a case where the bearing intends to detach from the shaft portion;
• and
• a reinforcing member extending in a direction intersecting a direction in which the shaft portion extends,
• wherein the shaft portion and the stopper-contacting portion are connected to the reinforcing member outside of both of opening ends of the bearing portion.