Electrochromic device

An electrochromic device comprising an electrochromic layer, the electrochromic layer containing a tungsten oxide material, the tungsten oxide material comprising potassium-containing tungsten oxide particles, the potassium-containing tungsten oxide particles having an average particle size of 100 nm or less, containing potassium within a range of 1 mol % to 50 mol %, and including a central section and a peripheral section adjacent to the central section, a periodicity of a crystal varying between the central section and the peripheral section,

• wherein the potassium-containing tungsten oxide particles have a crystal structure in which plural phases intersecting with a direction from inside toward a surface of the particles and being parallel to each other are sequentially arranged in the direction, and wherein an interatomic distance Ic between the plural phases adjacent to each other in the central section is different from an interatomic distance Ip between the plural phases adjacent to each other in the peripheral section.