An air purifier including an air sterilizing unit, an air blowing unit arranged such that air flows in the air sterilizing unit； the air sterilizing unit comprising housing and an ultraviolet light emitting device which emits deep ultraviolet rev having wavelength of 200 to 350 nm； the housing comprising a sterilizing room； the sterilizing room comprising an air intake opening and an air outlet opening； and the ultraviolet emitting device being arranged in the housing such that the deep ultraviolet, ray is emitted toward inside of the sterilizing room, wherein (A) at least a part of an inner wall surface of the sterilizing room comprises an ultraviolet reflective material which may be covered with an ultraviolet ray transmitting material, and/or (B) one or more reflector plate is arranged in the sterilizing room.
