An electrochromic device according to an embodiment includes a first transparent conductive layer, an ion storage layer, an electrolyte layer, an electrochromic layer, and a second transparent conductive layer. The electrolyte layer includes a tantalum atom. The electrochromic layer includes a tungsten atom. The ion storage layer includes an iridium atom and a tantalum atom. The ion storage layer is hydrogenated in bleached state and the electrochromic device has a transmittance of 64.1% or more in bleached state. A difference between the transmittance of the electrochromic device in bleached state and the transmittance of the electrochromic device in colored state is 8.4% or more.