An integrated composite electrode comprises a plurality of minute electrodes arranged over a substrate; and a wiring portion for applying an electric signal to the minute electrodes and extracting an electric signal from the minute electrodes. These minute electrodes have a porous conductive material on their surfaces and an impedance of 50 KΩ or less. Preferably, the porous conductive material is gold and is made by power supply of a current density of 1.0 to 5.0 A/dm<sp>2</sp> for 10 to 360 seconds. This integrated composite electrode can comprise minute electrodes arranged in a matrix over the substrate; lead wires connected with the minute electrodes; and a wiring portion including electric contacts connected with the ends of the lead wires.
