The purpose of this invention is to provide an electrode device for use in iontophoresis, in which an electrode layer for introduction of a medication can be attached to a medication reservoir by a simple method, and in which the medication reservoir can be reliably held when the medication is introduced into a patient.A main electrode layer 3 and a sub-electrode layer 1 are secured on a substrate 6 while both the layers are being insulated from each other. The main electrode layer 6 is for introduction of a medication, and the sub-electrode layer 1 is provided to hold the medication reservoir 5 on the substrate 6. The medication reservoir 5 is so disposed on the substrate 6 as to be in contact with the main electrode layer 1 and the sub-electrode layer 1. The medication reservoir 5 is a gel containing a halogen compound, and the sub-electrode layer 1 comprises a metal with a lower ionization tendency than a hydrogen atom. The medication reservoir 5 and the sub-electrode layer 1 are secured to each other by applying an electric current there through. In this way, the medication reservoir 5 can be firmly held on the substrate 6, while being kept in contact with the main electrode layer 3.
