Ta3N5 is a promising semiconductor photocatalyst which can generate H2 gas from water under visible light illumination. It is expected that Ta3N5 exhibits a strong anisotropy in its physical properties stemming from its highly anisotropic crystal structure. However, such anisotropic properties have not been verified experimentally due to the difficulty in synthesizing a large single crystal. Here, we report the synthesis of (010)-oriented Ta3N5 single-crystalline thin films by solid phase epitaxy on the (110) plane of perovskite LaAlO3 substrates. The obtained epitaxial thin films of Ta3N5 exhibited clear optical anisotropy (pleochroism) as predicted by previous first-principles calculations. The optical gap for E||[100] polarization (∼2.12 eV) was smaller than that for E||[100] polarization (∼2.27 eV).