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. The ionizer according to another embodiment includes a 3D substrate having a polygonal pillar shape in which polygonal planes are perforated an electrode unit including one or more electrodes formed on at least one inner surface of pillar planes forming the polygonal pillar to generate a positive ion or a negative ion and a coating part in which an inner surface facing the pillar plane with the electrode unit is coated with photocatalyst.
