Abstract: When an ionization section is taken out of a main body housing of a conventional air cleaner in order to wash the ionization section, an ionization line may be cut by being accidentally touched. In order to avoid this problem, a pre-filter (7) is mounted on a front surface of an ionization and dust collection unit (6) so as to be detachable. The pre-filter (7) is slidably guided by guide furrings (23) in a sub-frame (12), and is mounted on a front surface of the sub-frame (12). When the pre-filter (7) is mounted, ionization lines (15) are not exposed, so that the pre-filter (7) protects the ionization lines (15). When the ionization and dust collection unit (6) is detached from the main body housing, therefore, there is no problem that the ionization lines (15) might be cut by being accidentally touched with worker's hands, for example.