The present invention relates to a lighting device for disinfesting which can reliably disinfest the insect pests, such as the spider mites, etc. The lighting device for disinfesting comprises a light source and a control circuit carrying out the light control on the light source, and the light source radiates the ultraviolet rays containing wavelengths of 260-305 mm or having a peak wavelength in the wavelength range of 260-305 mm. The control circuit carries out the dimming control on the above light source, so that the radiation intensity of the ultraviolet rays emitted out by the light source changes along with time within a range of 0.1-50 microwatt/cm<2>, and changes repeatedly. Therefore, on the condition that the insect pests are the spider mites, the action of the spider mites are dull by the radiation of the ultraviolet rays at a low intensity, and then the ultraviolet rays radiate at a high intensity, so that the spider mites can be killed by radiating the high intensity ultraviolet rays to the spider mites continuously, and accordingly, the spider mites can be desinfested reliably. Moreover, by the repeated change of the radiation intensity of the ultraviolet rays, the disinfection effect can be improved reliably.
