In the fabrication of micrometer-sized structures from an epitaxial topological insulator thin film with photolithography, the film is usually deteriorated by the chemicals used in the process. By molecular beam epitaxy of (BixSb1-x)2Te3 topological insulator onto Hall bar-shaped plateaus pre-lithographed on SrTiO3 substrate, we have directly prepared Hall bar devices of epitaxial topological insulator thin film, avoiding the degradation of film quality in photolithography. Atomic force microscope and transport measurements have demonstrated that the Hall bar devices have the similar properties as that of (BixSb1-x)2Te3 films epitaxied on ordinary SrTiO3 substrates. The new microfabrication method can not only help to realize various novel quantum phenomena predicted in topological insulators but be applied to other epitaxial low-dimensional systems as well.