Highly electrically conductive indium-tin-oxide thin films were epitaxially grown on an extremely flat (100) surface of yttria-stabilized zirconia single-crystal substrates at a substrate temperature of 600^oC by a pulsed-laser deposition technique. A resistivity down to 7.7×10^-5 Ohmcm was reproducibly obtained, maintaining optical transmission exceeding 85% at wavelengths from 340 to 780 nm. The carrier densities of the films were enhanced up to 1.9×10²¹ cm^-3, while the Hall mobility showed a slight, almost linear, decrease from 55 to 40 cm²V^-1s^-1 with increasing SnO₂ concentration. The low resistivity is most likely the result of the good crystal quality of the films.