We have developed a low-temperature, high-magnetic-field scanning tunneling microscope combined with pulsedlaser deposition, and studied atomic-scale growth of SrTiO₃ (STO) and LaAlO₃ thin films. A (√13×√13 )-R33.7^o STO(001) substrate, prepared in oxygen atmosphere, is atomically resolved and plays a crucial role in elucidating the initialgrowth process. When homoepitaxial STO films were grown on the (√13×√13 ) substrate surfaces, additional TiO_x layer of the substrate was transferred to the film surfaces. Atomic-scale microscopic/spectroscopic approach opens up awayto atom-by-atom controlled oxide epitaxial films and heterostructures.