An electrochromic device (ECD) comprising two metal-complex-based electrochromic thin films individually acting as a working electrode and a counter electrode; (i) one of the two metal-complex-based electrochromic thin films being a film of a cathodically coloring metallo-supramolecular polymer comprising at least one organic ligand having a plurality of metal coordination positions and a metal ion of at least one transition metal and/or lanthanoid metal with the at least one organic ligand and the metal ion being arranged alternately, and the other of the two metal-complex-based electrochromic thin films being a film of an anodically coloring metal hexacyanoferrate (MHCF) represented by the formula: M(II) 3 [Fe(III)CN 6 ] 2 where M is at least one selected from Ni and Zn, and (ii) the electrochromic device having a configuration of a first conducting substrate; the film of the cathodically coloring metallo-supramolecular polymer; an electrolyte; the film of the anodically coloring metal hexacyanoferrate (MHCF); and a second conducting substrate being arranged in this order; wherein the at least one transition metal and/or lanthanoid metal comprises a metal selected from iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), europium (Eu) and terbium (Tb), and wherein the at least one organic ligand comprises an organic ligand having a structure represented by at least one of the following formulae: wherein R is a spacer comprising a carbon atom(s) and a hydrogen atom(s), or a spacer directly connecting the two moieties selected from terpyridyl group, bipyridyl group, pyridyl group, phenanthrolyl group, acetylacetonato group; and R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, an aryl group or an alkyl group. M(II) 3 [Fe(III)CN 6 ] 2 where M is at least one selected from Ni and Zn, and (ii) the electrochromic device having a configuration of a first conducting substrate; the film of the cathodically coloring metallo-supramolecular polymer; an electrolyte; the film of the anodically coloring metal hexacyanoferrate (MHCF); and a second conducting substrate being arranged in this order; wherein the at least one transition metal and/or lanthanoid metal comprises a metal selected from iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), europium (Eu) and terbium (Tb), and wherein the at least one organic ligand comprises an organic ligand having a structure represented by at least one of the following formulae: wherein the at least one transition metal and/or lanthanoid metal comprises a metal selected from iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), europium (Eu) and terbium (Tb), and wherein the at least one organic ligand comprises an organic ligand having a structure represented by at least one of the following formulae: wherein R is a spacer comprising a carbon atom(s) and a hydrogen atom(s), or a spacer directly connecting the two moieties selected from terpyridyl group, bipyridyl group, pyridyl group, phenanthrolyl group, acetylacetonato group; and R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom, an aryl group or an alkyl group. <EOS>