PURPOSE: To ensure the evolution of ozone gas and facilitate the startup of an air cleaner by providing an electric heater inside a plate-like dielectric.

CONSTITUTION: There are provided in an air passage an ozone adding part, a filter part 14 such as minipleat filter and an ozone killer 17 in that order from its upstream side. The ozone gas adding part is provided with an ozonizer fitted with a linear corona discharge electrode 5 and a plane inductive electrode 6 with a part of a plate-like dielectric 4 interposed therebetween and the plate- like dielectric 4 is also provided with an electric heater 7 in its interior. This permits a creeping discharge to be produced on the side of the linear corona discharge electrode 5 of the ozonizer immediately even after the startup of the air cleaner in a room high in humidity, thereby ensuring the evolution of the ozone gas and facilitating the startup of the air cleaner.