This invention provides an electrochromic device which has superior coloration repeat properties, high light transmittance and small thickness. A film is provided comprising a first electrode and second electrode in the same plane, and an electrochromic region and electrolyte region laminated in this plane. The electrochromic region is provided on the second electrode, the electrolyte region is provided on the first electrode, and the boundary between the electrochromic region and electrolyte region lies in the planar direction of the film.