may have a variety of detachable coupling ways with the catalyst part 130 according to the present invention the body 110 has a generally rectangular section but it may have free sections like circular and other sections the light source part 120 is fixed to the body 110 and serves to irradiate ultraviolet light the light source part 120 includes the led 121 and the substrate 122 to which the led 121 is fixed in fig4 an air flow direction is indicated by an arrow the led 121 serves to irradiate uva ultra violet a light or uvc ultra violet c light having a wavelength of 400 nm or under thus solving the problems in the use of the existing mercury vapor lamp and achieving effective light irradiation with small power in this case since the uva has a relatively low price it is advantageous in view of expense and effectively activates the photocatalytic reaction of a photocatalyst carrying medium contrarily the uvc has a relatively high price but it performs the activation in the photocatalytic reaction and the sterilization function to improve the sterilization efficiency two or more light source parts 120 may be provided according to the size of.