To purify air by not only removing dirt and dust in air but also removing harmful organic substances or the like in the air.

Both end faces in the longitudinal direction of a rectangular parallelepiped box body 1 whose inside is made hollow and to be an air flow path 2 are opened in an optional shape and communicated with the air flow path inside the box body. An air intake port is attained by attaching a dust removing filter 3 to one end face and an air discharge port is attained by attaching a motor-driven fan 5 to the end face on the opposite side. Also, the optional surface of the air flow path inside the box body is turned to a photocatalyst surface 7 coated with a titanium oxide and an ultraviolet ray lamp 8 is disposed at a position to irradiate the photocatalyst surface coated with the titanium oxide.