The present disclosure relates to an alternating bipolar ionizer. It is a plate-type structure consisting of a substrate, an emitter plate, a dielectric barrier plate, and a ground plate. The ground plate and the emitter plate form an electric field, and the electrons of the emitter plate are led out of the dielectric barrier plate on a grounding side of the electric field. Some electrons meet the grounding pole plate and flow into the ground plate to form a current, and some escape from the surface of the dielectric barrier plate and meet the indoor air molecules. When the escaped electrons reach a certain rate, the oxygen molecules can be excited to be an ionic state, and air quality can improve. When AC high-voltage current is inputted, the bipolar ions are generated alternately, so a bipolar ionized gas flow can be injected into the air to improve air quality.