The present disclosure relates to a stacked x-ray tube apparatus using a spacer, and more particularly, to a stacked x-ray tube apparatus using a spacer that makes it possible to reduce the size of an x-ray tube by forming a stacked structure, with electric insulation and predetermined gaps maintained for each electrode, by forming a stacked x-ray tube by inserting insulating spacers (for example, ceramic) between a exhausting port, a cathode, a gate, a focusing electrode, and an anode and bonding them with an adhesive substance, and then inserting a spacer between a field emitter on a cathode substrate and a gate hole connected with a gate electrode.