To reduce the number of part items and production cost in an air cleaner by dispensing with an ultraviolet radiation device, which is needed for generating negative ions by catalysis in the case of using a photocatalyst in the air cleaner, to simplify and miniaturize the structure of the air cleaner.

A catalytic reaction is caused by a flow of air instead of the photocatalyst, and a catalyst for releasing radicals or negative ions is used, whereby a device having an air cleaning effect can be constituted without requiring ultraviolet ray. Further, a filter with the catalyst adhered thereto is attached to the air outlet of an air cleaner, whereby the air cleaning effect can be further enhanced.