The present invention provides an electrochromic device in which a color during the coloring mode is gray. A lower ITO transparent electrode film 12 constituting a lower electrode film is formed on a transparent glass substrate 10. On the lower ITO transparent film 12, a nickel oxides film 32 constituting an oxidation coloring layer, a tantalum oxide film 16 constituting a solid-state electrolyte layer, a mixture film 34 of tungsten oxide and titanium oxide constituting a reduction coloring layer and an lower ITO transparent electrode film 20 constituting a upper electrode film are formed sequentially. The color during the coloring mode is gray and the color during the bleaching mode is achromatic.