We have investigated the local polarization switching behaviors of epitaxial (Bi1/2Na1/2)TiO3 (BNT) thin films obtained by a pulsed laser deposition (PLD). Using ozone gas as a deposition atmosphere of PLD, epitaxial growth of BNT films was achieved on SrRuO3/SrTiO3(1 0 0) electrode substrates. Piezoresponse force microscopy (PFM) revealed that BNT grains in the films have a single-domain structure without domain walls. These domain structures and the local polarization switching measured by PFM indicate that the oxidizing atmosphere of ozone gas is considered to suppress the generation of bismuth and oxygen vacancies in the deposited BNT layers. We propose that the PLD method using ozone is effective in obtaining high-quality single-phase BNT films with a less concentration of lattice vacancies.