We investigated leakage current characteristics affected by crystallinity and domain wall currents of epitaxial BTFO thin films on Nb-doped SrTiO3 substrates. The c-oriented BTFO thin film and BTFO thin films with a mixture of a-oriented and c-oriented crystallinity were prepared by controlling the substrate and PLD deposition rate. The c-oriented BTFO thin film exhibited the best leakage current characteristics because the Bi2O2 layers were placed perpendicular to the c-axis to reduce leakage currents. The BTFO thin films with a mixture of a-oriented and c-oriented crystallinity exhibited improved ferroelectric properties and piezoelectric properties compared to the c-oriented BTFO thin film. The current domains of the BTFO thin films corresponding to the ferroelectric domain structures were observed by a conducting atomic force microscope, and it was observed that leakage currents were formed around the domain walls. In particular, the largest leakage currents are formed at the boundaries of c-oriented domains and a-oriented domains, and these domain boundaries confirmed that BTFO thin films with a mixture of a-oriented and c-oriented crystallinity were responsible for the largest leakage currents.