PURPOSE: To obtain a counter electrode for a device that enables the formation of an electrochromic display device of less variances in coloring and erasing characteristics by forming an LixWO3 electrode on the conductive substrate by using the specific electrolytic reaction.

CONSTITUTION: A WO3 layer is formed on a conductive substrate excluding a part (portion a) thereof. On the other hand, the portion (a) mentioned above is brought into contact with a reactive metal M (Al, Ni, Co, etc.) and in this state the substrate is immersed in a soln. contg. Li ions. In the case of using a soln. of propylene carbonate of LiClO4 of, for example, about 1mol/l concentration as the above- mentioned soln., a battery system shown by the formula is formed and the equilibrium of reaction is reached in about 10 min, whereby the counter electrode formed with a blue-colored LixWO3 on the substrate is obtained. The electrochromic display device is formed by sandwiching electrolyte 4 comprising an Li salt soln. between the glass substrate 1 (desplay electrode) provided with a transparent conductor 2 and a transition metal oxide layer 3 and the above-mentioned couter electrode 5.