[Purpose] The purpose of this study was to evaluate the efficacy of tap water (drinking water) and normal saline (sodium chloride solution 0.9%) iontophoresis treatment for a patient with idiopathic hyperhidrosis [Subjects and Methods] In this study, tap water and normal saline iontophoresis were used to treat a 21 year-old female who was suffering from severe palmoplantar idiopathic hyperhidrosis. Post-iontophoresis sweat intensity of 8 treatment sessions were averaged and then normalized relative to the corresponding mean value which was obtained before iontophoresis treatment. [Results] The subject showed 24.72% and 42.01% decreases in sweat intensity following tap water and normal saline iontophoresis, respectively. [Conclusion] Tap water and normal saline iontophoresis are effective in the treatment of idiopathic hyperhidrosis. However, normal saline iontophoresis is 1.7 times more effective than tapwater iontophoresis at obstructing secretion.