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 including a housing and an ultraviolet light emitting device which emits deep ultraviolet ray having wavelength of 200 to 350 nm, the housing including a sterilizing room the sterilizing room including an air intake opening and an air outlet opening and the ultraviolet light 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 includes 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 wherein at least a part of the surface of the reflector plate which may be covered with an ultraviolet ray transmitting material includes an ultraviolet reflective material and the deep ultraviolet ray emitted from the ultraviolet light emitting device passes through air in the sterilizing room and thereafter further passes through the air in the sterilizing room once or more, by being reflected on the inner wall surface which includes the ultraviolet reflective material or on the surface of the reflector plate which includes the ultraviolet reflective material.
