A mirror rotating apparatus includes a stationary portion and a rotating portion. The stationary portion includes a detection sensor configured to detect rotation of the rotating portion. The rotating portion includes a mirror portion whose outside surface includes a plurality of mirror surfaces that face radially outward. The mirror portion includes a rotation detection surface opposite to the detection sensor, and a balance correction portion defined by a groove or a projection extending in a circumferential direction in the rotation detection surface. The balance correction portion locates a center of gravity of the mirror portion closer to the rotation axis. The rotation of the rotating portion causes the balance correction portion to pass through a region to which light is emitted from the detection sensor.