A austenite phase in the bainitic steel, martensite, and bainite - a separation method for visualizing ferrite matrix, the austenite phase and martensite phase in the bainitic steel to provide a discernible way in the nanoscale. The method of The present invention is, a) by electrolytic polishing the surface of the bainitic steel strip in an electrolytic solution containing corrosive acids and an organic solvent, forming a native oxide layer on the surface of the bainitic steel strip a step of, b) after completion of the electrolytic polishing, the electrolyte solution wherein the bainitic steel pieces in subsequently immersed, the area covering the martensite phase and the austenite phase of the native oxide layer, the respective and 1 and selectively forming a second corrosion product layer, c) subjecting the surface of the bainitic steel pieces in the scanning electron microscope observation by backscattered electron detector, said first and second corrosion to obtain a contrast between the product layer and the remaining surface, and the darkest areas of the austenite phase, the bainite - the brightest region ferrite matrix, the martensite phase It includes a step of visualizing, as the brightness of the region between the c) step is performed the incident energy of the primary electrons as follows 3 keV. .FIELD 1