Providing an electrode structure capable of realizing an electrode array which allows each of the electrodes to be individually controlled while allowing them to be densely arranged and placed in a living body. According to the present invention, an electrode control circuit electrically connected to an electrode body is fixed to a rear portion of the electrode body within a front-viewed contour of the electrode body. This electrode control circuit may be contained in a recess formed in the rear portion of the electrode body, or it may be fixed to the back face of the electrode body. Conversely, an electrically conductive material layer covering the electrode control circuit may be used as the electrode body. A plurality of such bioelectrodes may be arranged in a two-dimensional form on a substrate or connected by a connection line including an electrical wire. Such configurations allow the bioelectrodes to be densely arranged.