Disclosed is an optical unit wherein a rotating reflector rotates about a rotation axis in one direction, while reflecting light emitted from a light source. The rotating reflector is provided with a reflecting surface such that the light reflected by the rotating reflector, while rotating, forms a desired light distribution pattern, said light having been emitted from the light source. The light source is composed of light emitting elements. The rotation axis is provided within a plane that includes an optical axis and the light source. The rotating reflector is provided with, on the periphery of the rotation axis, a blade that functions as the reflecting surface.