A beam scanning apparatus includes a light source configured to emit light, and a reflective phased array device configured to reflect the light emitted from the light source and incident on the reflective phased array device, and electrically adjust a reflection angle of the reflected light reflected by the reflective phased array device, wherein the light source and the reflective phased array device are disposed such the light is incident on the reflective phased array device at an incidence angle with respect to a normal of a reflective surface of the reflective phased array device.