Provided is a preparation method for a thermoelectric composite. The preparation method for a thermoelectric composite comprises the steps of: preparing a base substrate containing a first binary metal oxide; and providing a metal precursor and a reaction material containing oxygen (O) onto the base substrate to form a material film containing a second biliary metal oxide resulting from the reaction of the metal precursor and the reaction material, wherein in the step of forming the material film, a 2-dimensional electron gas is generated between the base substrate and the material film as the material film is formed on the base substrate.