The present invention is having a characteristic of, even for a material for which deposition or wet coating is difficult in a state of a metal complex, co-deposition an organic compound (ligand) and a metal salt constituting raw materials of the metal complex to execute complex formation on a substrate thereby forming a film containing such metal complex and preparing an electroluminescent device utilizing thus formed co-decomposition film. The aforementioned organic compound (ligand) is required to have a functional group easily releasing a proton to show anionic property (thus bonding with a metal), and a functional group having a non-covalent electron pair for coordination bonding with a metal.