A vehicle seat equipped with a side airbag apparatus and method thereof that even if a pad side face portion and pad rear face portion of a seatback pad are disposed at a vehicle width direction outer side and vehicle rearward side of a side frame at a side opposing a vehicle body side portion, improve assembly operations. Since the diffractive optical element uses the composite material containing the resin and the inorganic particles as a material for the diffraction grating, which is relatively difficult to process, the moldability improves compared with the conventional case of using glass, etc. The isolated epitaxial region is electrically coupled to at least one of the bond pad and the ground pad.