The present disclosure discloses metal oxide nanoparticle ink, a method of preparing the same, a metal oxide nanoparticle thin film manufactured using the same, and a photoelectric device using the same. The method of preparing metal oxide nanoparticle ink according to an embodiment of the present disclosure includes a step of, using a ligand solution including a metal oxide and an organic ligand, synthesizing a first nanoparticle that is a metal oxide nanoparticle surrounded with the organic ligand; a step of preparing a dispersion solution by dispersing the first nanoparticle in a solvent; a step of preparing a second nanoparticle by mixing the dispersion solution and a pH-adjusted alcohol solvent and then performing ultrasonication treatment to remove the organic ligand surrounding the first nanoparticle; and a step of preparing metal oxide nanoparticle ink by dispersing the second nanoparticle in a dispersion solvent.