A HOUSING HAVING A SUCTION PORT AND A DISCHARGE PORT, AN IMPELLER (21) AND A CASING (22) THAT HOUSES THE IMPELLER (21), AN AIR BLOWER (2) HOUSED IN THE HOUSING, A FILTER THAT LETS THROUGH THE AIR SUCTIONED FROM THE SUCTION PORT BY THE AIR BLOWER (2), AND TWO ION GENERATING SECTIONS THAT GENERATE POSITIVE AND NEGATIVE IONS ARE PROVIDED. THE ION GENERATING SECTION IS ARRANGED ON A CIRCULAR-ARC GUIDE WALL (2A) IN THE CASING (22). THE POSITIVE AND NEGATIVE IONS GENERATED BY THE ION GENERATING SECTION ARE EFFICIENTLY INCLUDED IN THE AIR PASSING THROUGH AS LAMINAR FLOW ALONG THE CIRCULAR ARC GUIDE WALL (22A). (FIG. 4)
