The present invention provides an electrode device used iniontophoresis treatment, in which an electrode layer usedfor introduction of medication can be contacted to amedication reservoir layer in a simple manner, and in whichthe medication reservoir layer can be reliably held whenthe medication is introduced into skin. A main-electrodelayer and a sub-electrode layer are secured on a substratewhile both the layers are being insulated from each other.The main-electrode layer is intended for introduction ofthe medication, and the sub-electrode layer is provided tohold the medication reservoir layer 5 on the substrate.The medication reservoir layer is located on the substrate,to be in contact with the main-electrode layer and the sub-electrodelayer, and is a gel containing halogen compound.The sub-electrode layer comprises a metal having a lowerionization tendency than hydrogen. Themedicationreservoir layer and the sub-electrode layer are bonded toeach other by applying an electric current to both layers,to firmly hold the medication reservoir layer on thesubstrate, while being kept in contact with the main-electrodelayer.
