Balneotherapy has been widely used for the treatment of skin diseases in the world. The purpose of this study was to determine the bath effect of the alkaline reduced spring water with the properties of high pH and low oxidation reduction potential (ORP) on the skin injury induced by ultra violet (UV) irradiation. For this purpose, hairless mice were irradiated with UV-B to cause skin injury, and individually taken a bath in spring water (experimental group) and tap water (control group) once a day for 40 min during 21 days. We observed histological changes of the back skin through macro- and microscopic methods compared to the control group. We found that skin injury of the experimental group was more quickly recovered than that of the control group. Under the light microscope, the experimental group showed that epidermal thickening (p<0.01) and the mast cell activation (p<0.001) were lower compared with the control group, in addition infiltration of inflammatory cells and degranulation of mast cells were less observed. These results suggest that regular bath in the spring water with the properties of high pH and low ORP has a positive effect on the skin injury induced by UV irradiation.