PURPOSE: To quickly analyze a plurality of samples by providing a reference electrode and a counter electrode in a container and a means which supplies a prescribed voltage during each measurement and measuring an electric current which flows during the measurement.

CONSTITUTION: A plurality of the same electrodes 12-19 each of which is composed of a rod-like conductive inert material buried in a nonconductive inert material, such as Teflon, etc., is arranged in a container 11. It is preferable to constitute the electrodes 12-19 so that the electrodes 12-19 can have means which rotate in the axial direction shown by arrows 20 and 21 in the figure. This measuring system contains a microcomputer 22 coupled with a potentiostat 23 through a D/A port. The electrode assembly is connected to the potentiostat 23 and, at the same time, to the parallel port 25 of the computer 22 through a multiplexer 24. The container 11 houses a reference electrode 26 and a counter electrode 27 connected to the potentiostate 23. In this operating method, a potential is supplied to a working electrode and a generated current is measured. Therefore, a plurality of samples can be analyzed quickly.