In late years, a health benefit of the hydrogen water was reported, and a lot of fundamental researches and clinical trials came to be performed in Japan.Particularly, it spreads out for the clinical application because hydrogen water removes the active oxygen which is harmful to a body.Reduced water by electrolysis is beneficial for Health with hydrogen, and the research on functional hydrogen water, especially on reduced water is developing at a rapid pace in Japan.Reduced water such as electrolyzing hydrogen water can scavenge reactive oxygen species in human body.This hydrogen waters are expected to have preventive and positive effects on oxidative stress-related diseases such as diabetes, cancer, arteriosclerosis, high blood pressure, apoplexy and aging.