In an air cleaner, there are some problems. For example, when an ionization section is taken out of a main body housing in order to wash the ionization section, an ionization line is cut by being erroneously touched. A pre-filter 7 is mounted on a front surface of an ionization and dust collection unit (an ionization section) 6 so as to be detachable. The pre-filter 7 is guided by a guide furring 23 in a sub-frame 12 and slid, and is mounted on a front surface of the sub-frame 12. When the pre-filter 7 is mounted, the ionization line 15 is not exposed, so that the pre-filter 7 protect the ionization line 15. When the ionization and dust collection unit 6 is detached form the main body housing, therefore, there is no problem that the ionization line 15 is cut by being erroneously touched with worker's hands, for example.