Disclosed is an electrochromic device that includes a first electrode and a second electrode facing each other, an electrochromic layer between the first electrode and the second electrode, and an electrolyte between the first electrode and the second electrode and being in contact with the electrochromic layer. The electrochromic layer may include a plurality of oxide semiconductor particles, a metal oxide on the surface of the oxide semiconductor particles, and an electrochromic material. An energy bandgap of the oxide semiconductor particles is in a range of about 3 eV to about 5 eV and an energy bandgap of the metal oxide is in a range of about 3 eV to about 5 eV, and a difference of conduction band energy levels of the oxide semiconductor particles and the metal oxide is about 0.5 eV or less. A method of manufacturing the electrochromic device may also be provided.