In an ionizer composed of an electrode needle cartridge and a main body block, the electrode needle cartridge is provided with an electrode needle for generating an ion, a high voltage generating device for applying high voltage to the electrode needle, and a receiving connector for connecting a feeding connector, and the main body block is provided with an air-blowing outlet serving as an electrode needle housing portion, an air passing-through hole for supplying air to the air-blowing outlet, and a connecting port for connecting an air piping. The electrode needle cartridge is configured such that when the electrode needle cartridge and the main body block are connected or separated, the electrode needle is inserted into or removed from the air-blowing outlet from a rear end portion side of the air-blowing outlet.