In the air purifier, in order to clean the ionization part, when taking it out from the main body casing, there are troubles such as accidentally touching the ionization line and breaking the ionization line. A prefilter 7 is detachably attached to the front of the ionization / dust collection unit (ionization unit) 6 . The prefilter 7 is guided and slid by the guide rail 23 of the subframe 12, and is installed in front of the subframe 12. If the pre-filter 7 is installed, the ionization line 15 will not be exposed, and the pre-filter 7 protects the ionization line 15. Therefore, when the ionization and dust collection unit 6 is detached from the main body casing, hands and the like will not touch the ionization line 15 carelessly, and there is no trouble such as breaking the ionization line 15 .