A beam scanning apparatus comprising: 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 reflected light reflected by the reflective phased array device, wherein the light source and the reflective phased array device are disposed such that 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, and wherein the reflective phased array device comprises a plurality of antenna resonators, each of the plurality of antenna resonators being independently driven, and wherein each of the plurality of antenna resonators comprises: an electrode layer; an active layer disposed on the electrode layer; an insulating layer disposed on the active layer opposite to the electrode layer; and an antenna layer disposed on the insulating layer opposite to the active layer, wherein the antenna layer comprises a plurality of antenna layers, and wherein each of the plurality of antenna layers extends in a first direction and the plurality of antenna layers are disposed at predetermined intervals in a second direction perpendicular to the first direction, and wherein the reflected light comprises directly reflected light that is directly reflected by the reflective phased array device and resonated scattered light that is generated based on resonance in each of the plurality of antenna resonators of the reflective phased array device, and characterised in that at least one of an interval between the plurality of antenna layers in the second direction and an antenna period is determined such that an intensity of the directly reflected light is equal to an intensity of the resonated scattered light, and in that the antenna period is a length at which the plurality of antenna layers are repeated in the second direction. 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 reflected light reflected by the reflective phased array device, wherein the light source and the reflective phased array device are disposed such that 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, and wherein the reflective phased array device comprises a plurality of antenna resonators, each of the plurality of antenna resonators being independently driven, and wherein each of the plurality of antenna resonators comprises: an electrode layer; an active layer disposed on the electrode layer; an insulating layer disposed on the active layer opposite to the electrode layer; and an antenna layer disposed on the insulating layer opposite to the active layer, wherein the antenna layer comprises a plurality of antenna layers, and wherein each of the plurality of antenna layers extends in a first direction and the plurality of antenna layers are disposed at predetermined intervals in a second direction perpendicular to the first direction, and wherein the reflected light comprises directly reflected light that is directly reflected by the reflective phased array device and resonated scattered light that is generated based on resonance in each of the plurality of antenna resonators of the reflective phased array device, and characterised in that at least one of an interval between the plurality of antenna layers in the second direction and an antenna period is determined such that an intensity of the directly reflected light is equal to an intensity of the resonated scattered light, and in that the antenna period is a length at which the plurality of antenna layers are repeated in the second direction. an electrode layer; an active layer disposed on the electrode layer; an insulating layer disposed on the active layer opposite to the electrode layer; and an antenna layer disposed on the insulating layer opposite to the active layer, wherein the antenna layer comprises a plurality of antenna layers, and wherein each of the plurality of antenna layers extends in a first direction and the plurality of antenna layers are disposed at predetermined intervals in a second direction perpendicular to the first direction, and wherein the reflected light comprises directly reflected light that is directly reflected by the reflective phased array device and resonated scattered light that is generated based on resonance in each of the plurality of antenna resonators of the reflective phased array device, and characterised in that at least one of an interval between the plurality of antenna layers in the second direction and an antenna period is determined such that an intensity of the directly reflected light is equal to an intensity of the resonated scattered light, and in that the antenna period is a length at which the plurality of antenna layers are repeated in the second direction.