An environmentally friendly method for preparing zinc oxide nanoparticle sol having more than 90% visible light transmission at 20 wt % solid; comprises of the neutralizing, under specific pH, an inorganic zinc salt with an inorganic alkali, both dissolved in ethylene glycol, and thermally aging the precipitates afterward. The light irradiation section is placed at one side surface of a main body of the beauty device, and the ion generating section is placed at the other side surface of the main body of the beauty device. The spool shaft is rotatably supported at an end thereof by the shaft support part.