Provided is an ionizer. In an embodiment, concaves-convexes are formed on a surface of a substrate, one or more electrodes for generating a positive ion or a negative ion is formed, and the concaves-convexes are coated with photocatalyst. The electrode is formed on a surface opposite to the surface on which the concaves-convexes are formed, and two or more substrates are disposed in line at an interval while the electrode and the concave-convex face each other. One or more pillar planes forming a polygonal pillar in which polygonal planes facing each other are perforated form the substrate, the one or more electrodes are formed on at least one inner surface of the pillar planes, and the pillar plane forming the substrate faces the pillar plane the electrode. The pillar plane forming the substrate and the pillar plane the electrode are alternately disposed.
