The capabilities and applications of the focused ion beam (FIB) technology for detection of an electrochemical signal in nanoscale area are shown. The FIB system, enabling continuous micro- and nanofabrication within only one equipment unit, was used to produce a prototype of electrochemical nanometer-sized electrode for sensor application. Voltammetric study of electrochemically active compound (ferrocenemethanol) revealed the diffusion limiting current (12 pA), corresponding to a disc (planar) nanoelectrode with about 70 nm diameter of contact area. This size is in a good accordance with the designed contact-area (50 nm × 100 nm for width × thickness) of the FIB-produced nanoelectrode. It confirms that produced nanoelectrode is working properly in liquid solution and may enable correct measurements in nanometer-sized regions.